PubMed Health⌕ Search

Biomedical subjects

Timothy D Smith

Publications and source records attributed to Timothy D Smith.

23 records · Page 2Linked to original sources
PubMed2002

Histological definition of the vomeronasal organ in humans and chimpanzees, with a comparison to other primates.

The vomeronasal organ (VNO) is a chemosensory structure that has morphological indications of functionality in strepsirhine and New World primates examined to date. In these species, it is thought to mediate certain socio-sexual behaviors. The functionality and even existence of the VNO in Old World primates has been debated. Most modern texts state that the VNO is absent in Old World monkeys, apes, and humans. A recent study on the VNO in the chimpanzee (Smith et al., 2001b) challenged this notion, demonstrating the need for further comparative studies of primates. In particular, there is a need to establish how the human/chimpanzee VNO differs from that of other primates and even nonhomologous mucosal ducts. Histochemical and microscopic morphological characteristics of the VNO and nasopalatine duct (NPD) were examined in 51 peri- and postnatal primates, including humans, chimpanzees, five species of New World monkeys, and seven strepsirhine species. The nasal septum was removed from each primate and histologically processed for coronal sectioning. Selected anteroposterior intervals of the VNO were variously stained with alcian blue (AB)-periodic acid-Schiff (PAS), PAS only, Gomori trichrome, or hematoxylin-eosin procedures. All strepsirhine species had well developed VNOs, with a prominent neuroepithelium and vomeronasal cartilages that nearly surrounded the VNO. New World monkeys had variable amounts of neuroepithelia, whereas Pan troglodytes and Homo sapiens had no recognizable neuroepithelium or vomeronasal nerves (VNNs). Certain unidentified cell types of the human/chimpanzee VNO require further examination (immunohistochemical and electron microscopic). The VNOs of P. troglodytes, H. sapiens, and New World monkeys exhibited different histochemistry of mucins compared to strepsirhine species. The nasopalatine region showed great variation among species. It is a blind-ended pit in P. troglodytes, a glandular recess in H. sapiens, a mucous-producing duct in Otolemur crassicaudatus, and a stratified squamous passageway in all other species. This study also revealed remarkable morphological/histochemical variability in the VNO and nasopalatine regions among the primate species examined. The VNOs of humans and chimpanzees had some structural similarities to nonhomologous ciliated gland ducts seen in other primates. However, certain distinctions from the VNOs of other primates or nonhomologous epithelial structures characterize the human/chimpanzee VNO: 1) bilateral epithelial tubes; 2) a superiorly displaced position in the same plane as the paraseptal cartilages; 3) a homogeneous, pseudostratified columnar morphology with ciliated regions; and 4) mucous-producing structures in the epithelium itself.

Aged↗
PubMed2002

Coronal suturectomy does not cause acute postoperative displacement in the cranial bases of craniosynostotic rabbits.

Approximately 300 to 500 infants per 1,000,000 have prematurely fused cranial sutures (craniosynostosis). Craniosynostosis can result in increased intracranial pressure and craniofacial deformities, which often require extensive and costly craniofacial surgery. Because the neurocranium and basicranium are developmentally interrelated, understanding their influence on one another is important for surgical planning. Although surgery has been found to have long-term effects on the cranial bases of craniosynostotic human beings and rabbits, the biological mechanisms behind these effects remain uncertain. Some researchers have suggested that the surgical release of synostosed sutures alters long-term growth patterns, resulting in cranial base differences between craniosynostotic individuals who undergo surgery and those who do not. Additionally, some investigators have proposed that an acute and surgically related displacement of basicranial elements may contribute to the observed differences. The current study examines acute postoperative changes in four lengths, three angles, and three triangles between cranial base landmarks in a sample of seven New Zealand white rabbits with familial nonsyndromic craniosynostosis. Results indicate that suturectomy caused no statistically significant (P < 0.05) acute length, angular, or shape differences in the cranial base. Thus, previous long-term cranial base differences found between rabbits that were operated on and those that were not were probably not caused by an acute displacement of skeletal elements as a result of surgery. These findings suggest that postoperative cranial base changes may be related more to chronically altered growth patterns than to acutely altered changes in intracranial pressure or dural tension.

Acute Disease↗
PubMed2002

Mandibular form in a rabbit model of familial nonsyndromic coronal suture synostosis.

Nonsyndromic coronal suture synostosis produces predictable and well-documented morphologies of the cranial vault with anteroposterior growth restrictions and mediolateral compensatory growth. The potential effects of nonsyndromic coronal suture synostosis on mandibular form are not as clear, however. This study was designed to evaluate whether coronal suture synostosis is associated with alterations in mandibular form by using a familial rabbit model of coronal suture synostosis. To assess this potential relation, the following hypothesis was tested: mandibular form in rabbits with coronal suture synostosis is significantly (P < 0.05) different from that seen in normal rabbits. The cleaned and dried mandibles of 33 adult New Zealand white rabbits were used (12 from normal rabbits, 13 from rabbits with delayed-onset synostosis, and 8 from rabbits with complete coronal suture synostosis). Seven anatomical landmarks on the mandible were located and digitized in three dimensions: anterior molar on the alveolus, posterior molar on the alveolus, coronoid process, anterior pole of the condyle, condylar process, angular process, and mandibular angle. To describe the mandibular condyle, the distance from the anterior pole to the posterior pole of the condyle was measured with digital sliding calipers, as was the distance between the medial and lateral poles. A shape ratio was then created using the dividend of these sums. Statistical analyses of mean form differences between mandibles were executed using Euclidean distance matrix analysis. Statistical analyses of the mandibular condyle linear and shape measurements were analyzed using one-way ANOVA in the three groups. Results showed that complete coronal suture synostosis is associated with significant (P < 0.05) differences in mandibular form compared with that of normal rabbits but that mandibular form in rabbits with delayed-onset synostosis does not differ from that of normal rabbits (P > 0.05). In particular, distances involving the coronoid process in rabbits with coronal suture synostosis were significantly different, paralleling previous work in human patients with coronal synostosis. There are no intrinsic condylar linear or shape differences between any of these groups, however. The form difference noted is most likely secondary to the synostosed coronal suture and may reflect alterations in the cranial base or masticatory musculature in this rabbit model.

Analysis of Variance↗
PubMedDate not supplied

The human vomeronasal organ: part IV. Incidence, topography, endoscopy, and ultrastructure of the nasopalatine recess, nasopalatine fossa, and vomeronasal organ.

BACKGROUND: Previous reports on the human vomeronasal organ (VNO) have been inconsistent. Observations of fossae on the nasal septum have been reported as the VNO. METHODS: Adult human subjects (210) and cadavers (31) were examined using rigid nasal endoscopy, serial histology, and biopsy ultrastructure (5). RESULTS: The nasopalatine fossa (NPF) and the nasopalatine recess (NPR) are discrete, but variable, structures located adjacent to the VNO region. The NPF is not a vomeronasal pit. A septal mucosal pit could hide the vomeronasal duct opening. The VNO is a submucosal structure located 2-8 mm superior to the NPR and cannot be positively identified either macroscopically or endoscopically. CONCLUSION: The VNO has long been mistaken for the NPF and septal mucosal pits. We show that serial histology is the correct method for identifying the VNO.

Chemoreceptor Cells↗