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Biomedical subjects

E D Shields

Publications and source records attributed to E D Shields.

35 records · Page 2Linked to original sources
PubMed1977

Tricho-dento-osseous syndrome: a scanning electron microscopic analysis.

A large kindred of which multiple members have the Tricho-dento-osseous syndrome is presented. This is an autosomal dominant disorder characterized by defective enamel, taurodontia, unusually curly hair and occasionally mild to moderate skeletal osteosclerosis. Histologic investigation of teeth (by both LM and SEM) demonstrated that there is a uniformly thin enamel covering with randomly distributed depression and pits. The mineral content of this enamel is closer to that of the underlying dentin, which accounts for its lack of radiographic contrast. The dentin was normal. A bizarre finding is that of a periradicular sheath or membrane that enclosed the open apices and extended partway up the root. It was composed of collagen fiber bundles. The anatomical position of this membrane suggested that it may represent the developing peridontal ligament seen in early tooth formation. Recent embryologic evidence provides support for mesenchymal culpability for all reported features of the syndrome.

Adolescent↗
PubMed1976

Allelic restriction: a biologic alternative to multifactorial threshold inheritance.

Contrary to the argument regarding the conservatism of the multifactorial threshold model for describing the inheritance of congenital malformations, little biological insight has resulted from the series of tautological, albeit grandiose, mathematical assumptions currently comprising the basis for this hypothesis. The working hypothesis of this presentation is to apply the "allelic restriction" model to the genesis of common human congenital malformations. New population data concerning isolated cleft palate closely fit the predictions of the proposed hypothesis. Recognising the heterogeneity of cleft palate as well as other common congenital malformations (namely, the difference between phenocopies, definable syndromes, and true hereditary cases), the "allelic restriction" model accords with the apparent greatly "reduced penetrance" of the heriditary cases. This model is meant to apply only to those congenital malformations which have both a high population frequency and a relatively small number of families showing an atypical type of vertical transmission.

Adult↗
PubMed1976

Periodontosis: a phenotypic and genetic analysis.

Two families who provide additional data concerning the metabolic, radiographic, and clinical parameters of periodontosis are presented. These findings include decreased serum alkaline phosphatase levels with absent liver isozyme fractions, decreased tubular bone over-all width and medullary space with relatively increased cortical area, and at least one case of primary dentition alveoloclasia with no permanent dentition alveoloclasia. In addition, a segregation analysis was performed on these two families and all completely reported families found in the literature. The results indicate that periodontosis is most probably inherited as an X-linked, dominant trait with decreased penetrance but relatively consistent gene expressivity. The female: male ratio of affected persons is approximately 2:1, and there is an over-all deficiency of males in these affected families.

Female↗
PubMed1976

Aarskog syndrome: new oral-facial findings.

The Aarskog syndrome is characterized by short stature with typical facial, digital and genital anomalies. A further case is reported which presented with the uncommon finding of ophthalmoplegia and three previously unreported oral-facial findings: enamel dysplasia, a "col" deformity of the anterior mandible and a paresis of the facial muscles innervated by the VII cranial nerve. The implications of genetic heterogeneity in this nosologic classification are discussed.

Abnormalities, Multiple↗
PubMed1975

Orofaciodigital syndrome, type I: a phenotypic and genetic analysis.

An additional family with the orofaciodigital syndrome. Type I, is presented. On the basis of previously published pedigrees, as well as the present case, data are presented that conclusively support an X-linked dominant mode of inheritance. Segregation analysis demonstrated that not only is there lethality in the male but there is significant lethality in the female due to lyonization. In addition, a review of the familial cases will demonstrate a large degree of intra- and interfamilial variation.

Abnormalities, Multiple↗
PubMedDate not supplied

Australian aborigines represent the first branch from Eurasian antecedents: odontometric evidence.

Most genetic data suggest that Australian aborigines and Southeast Asians associate, but their relative evolutionary relationship has remained obscure. Historically, the study of tooth crown variables has been important in establishing phylogenetic relationships. Through the quantification of whole tooth structure (GDP), including root, pulp, and enamel, a likely Eurasian phylogeny emerged from a canonical discriminant analysis of the microevolution among the populations. The analysis suggested that in modern human evolutionary history, Australian aborigines are the best representative extant population (first branch) from an unknown antecedent Eurasian founder population. The next branch from the Asian-based antecedent population was Caucasoids. Within the resident antecedent East Asian population, Southeast Asians then evolved, followed by a branch that lead to antecedent east Central Asians. Mongolians and all Native Americans independently evolved from this antecedent east Central Asian population. The relatively short morphogenetic separation between two areas that have been isolated for great periods of time, i.e., Australian aborigines and Native Americans, suggests that their association is not due to gene flow.

Asia↗
PubMedDate not supplied

A new perspective of human origin and dispersals derived from the microevolution of teeth.

Recent genetic studies have heightened the expectation that the origin of modern humans will be defined, but one clear vision has yet to be developed. The study of teeth has historically been an informative means to help define human dispersals. Quantitative tooth data is presented encompassing worldwide human populations. A null hypothesis phylogeny developed from the multivariate analysis of the microevolution of the dental phenotype was interpreted to be broadly in accord with the dominant interpretation of genetic, archaeological, and other dental data by showing that the first division in the dispersion of extant humanity was within sub-Sahara Africans; i.e., San, and Western Africans and Bantu. This "out-of-Africa" interpretation of the graphical results suggests that the first modern human African emigrants not to go extinct were Southeast Asian Negritos. All Eurasians then emerged and expanded through a series of extinct antecedent populations branching from the short lineage extending from Negritos to Australian aborigines. Caucasoids were the first group to fission from this stock. Under this hypothesis, the next to have emerged were antecedent Southeast Asians, from which present Southeast Asians and then antecedent east Central Asians then diverged. Independently, people from the region of Mongolia and all Native Americans arose as daughter populations from antecedent east Central Asians. The broad outline of humanity studied here cannot disprove the equally explanatory protean multiregional hypotheses, but with the inclusion of hominids and further modern human populations either parts of the multiregional hypothesis or the outlined more linear evolutionary scenario likely can be refuted.

Biological Evolution↗
PubMedDate not supplied

Chimpanzees as an outgroup for the examination of human dental evolution.

In the assessment of human origins, chimpanzees (Pan troglodytes, henceforth called Pan) represent the best hominoid outgroup for comparisons. Such an outgroup roots the "anatomically modern" human population cluster, or continuum. This study incorporates chimpanzees into a worldwide modern human database of quantified complete tooth variables (approximately 30 per tooth; e.g., root, pulp, enamel) in an attempt to develop a more accurate phylogeny of the hominoid continuum, with only intervening extinct hominids missing. Canonical discriminate analysis was performed mainly among Liberian common chimpanzees and global samples of humans. The first canonical variable explained 70% of the total variance and showed a tight cluster of humans, with chimpanzees as a distant outgroup. Within the human community, first non-San Bushman, sub-Saharan Africans and Andamanese, and then, close in, Australian aborigines were positioned towards Pan. Their relative orientation suggested an African human origin with the first branch within sub-Saharan Africa: sub-Saharan Africans and San Bushmen. Next, Andamanese Negritos, and then Australian aborigines, formed the early first surviving modern human lineage to leave Africa. Thin enamel and big teeth with relatively large roots characterized Pan nonmolar teeth. Humans showed a generalized sexual dimorphism for all teeth, with males having bigger teeth, bigger relative roots, and thinner enamel than females, while only Pan canines had significant and impressive sexual dimorphism. Interestingly, Pan molars were not larger than human molars. The data suggest that although hominids underwent two dental macroevolutionary events, the lineage leading to modern humans only experienced anterior tooth-size reduction. The suggested evolutionary significance of the observed total tooth variation is discussed.

Analysis of Variance↗
PubMedDate not supplied

Cavitation defects on the lingual ramus: a further expression of Stafne's defect.

Seven archaeological examples of 6,700 mandibles examined were found to have developmental cortical defects on the ramus. The defects, unusual in their position, were grossly and radiographically similar to developmental bone cavities (Stafne's) located in the sublingual region. Of the seven ramus defects, all of which were in adult males, six were in Alaskan Eskimos from Kodiak Island (N = 5) and Nelson Island (N = 1), and one was in a native American from Arkansas. Only five adult males from Finland have been reported with similar defects. A statistical examination of the metrics defining mandibular cavitation defects, along with prevalence data, suggest that the seemingly rare findings of ramus defects are an extreme manifestation of the continuum of severity of the Stafne's defect. Bilateral Stafne's defects also represent a severe manifestation.

Adult↗
PubMedDate not supplied

Salivary glands and human selection: a hypothesis.

Stafne static bone defect (SSBD) of the mandible is the only described destructive bone lesion that is highly localized, nonprogressive, but nonhealing. This common defect in male is found in the region of the major salivary glands that produce a cornucopia of biologically active factors. We describe rare phenocopies caused by mandibular immobility that hold the gland in a constant position thus implicating a localized chronic "leak" of an osteoclast induction factor from the major salivary glands as the pathologic agent. This finding suggests that increased salivary gland size could simulate immobility by apposing the gland to bone, thus allowing the "leaked" factor's gradient to have an effect. In one step, the putative genetic enlargement of a critical gland that produces many factors important for survival, a broad biological vista would be available to the massive potential for both positive and negative selection. Positive selection was identified by observing a correlation between the prevalence of enhanced androgen-induced enlarge salivary glands (SSBD) as a marker, with a great preponderance of males) and the conjectured resulting increased production of immunoreactive factors, with pole-to-equator isotherm and broad ranged infection clines. Negative selection was observed among the slave ancestors of African Americans for a potential embryonic homeotic mutation causing larger salivary glands in both sexes (decreased prevalence of SSBD, with an equal sex ratio). The decreased production of saliva and electrolytes diminished the salt and water depletive effects of severe diarrhea and vomiting induced by enteric diseases, which killed many slaves. Data presented suggests that SSBD is a polymorphism and a marker of selection processes that cause variation in size, or structure, of the major salivary glands.

Adult↗
PubMedDate not supplied

Quantitative complete tooth variation among east Asians and Native Americans: developmental biology as a tool for the assessment of human divergence.

The quantification of total tooth structure derived from X-rays of Vietnamese, Southern Chinese, Mongolians, Western Eskimos, and Peruvian pre-Inca (Huari Empire) populations was used to examine dental divergence and the morphogenetics of change. Multivariate derived distances between the samples helped identify a quasicontinuous web of ethnic groups with two binary clusters ensconced within the web. One cluster was composed of Mongolians, Western Eskimos, and pre-Inca, and the other group consisted of the Southern Chinese and Vietnamese. Mongolians entered the quasicontinuum from a divergent angle (externally influenced) from that of the Southeast Asians. The Chinese and pre-Inca formed the polar samples of the distance superstructure. The pre-Inca sample was the most isolated, its closest neighbor being the Western Eskimos. Univariate and multivariate analyses suggested that the pre-Inca, whose ancestors arrived in America perhaps approximately 30,000 years ago, was the least derived sample. Clearly, microevolutionary change occurred among the samples, but the dental phenotype was resistant to environmental developmental perturbations. An assessment of dental divergence and developmental biology suggested that the overall dental phenotype is a complex multigenic morphological character, and that the observed variation evolved through total genomic drift. The quantified dental phenotype is greater than its highly multigenic algorithm and its development homeostasis is tightly controlled, or canalized, by the deterministic organization of a complex nonlinear epigenetic milieu. The overall dental phenotype quantified here was selectively neutral and a good character to help reconstruct the sequence of human evolution, but if the outlying homeostatic threshold was or will be exceeded in antecedents and descendants, respectively, evolutionary saltation occurs.

Analysis of Variance↗
PubMedDate not supplied

The origin of Europeans is not rooted in the Middle East but in southern east Asia.

The study of tooth crown variables has proven useful in the assessment of human origin and dispersal. I show that multivariate analysis of quantified total tooth structure from dental X-rays is a powerful phylogenetic methodology. From an analysis of the complex global dental phenotype ("GDP," composed of approximately 30 root, pulp, crown, and enamel variables per tooth), a representative Western European population was found to associate with Southeast Asians, while Mongolians formed a tight cluster with all Native Americans. The results suggest that either an emigrant wave, or waves, of modern humans emerged from Africa and with time segregated into at least three groups: Australian aborigines, Europeans, and Southeast Asians, or less likely due to genetic and archaeologic observations, a southern Asia origin of all modern humans from an emigrant African hominid. Both hypotheses portend an early evolution of the European genotype and support the argument that Europeans are principally derived from Upper Paleolithic hunter-gatherers, and thus Middle East Neolithic people did not have a major genetic impact on Europeans.

Asia, Southeastern↗
PubMedDate not supplied

Does a parasite have a better chance of survival if an Inuit or a Mayan spits on it?

An earlier puzzling observation [Shields and Mann, J Craiofac Genet Dev Biol, 16:126-136, 1996] that the prevalence of a polymorphic male predominate, major salivary gland-associated, static lesion of the mandible increased exponentially from the Arctic to the Tropics was explained by both positive and negative selection (balancing) on major salivary gland endocrine and exocrine factors. Additional prevalence rates presented here identified three high prevalence high-Temperate zone cultures that were unusually exposed to alimentary parasites. A correlation between macroparasite exposure and the mandibular lesion helped refine the potential selective forces that fashioned major salivary gland size variation. The data suggests that positive selection occurred for androgen-induced enlargement of the suite of major salivary glands and consequently increased quantities of factors. Increased quantities of salivary gland biologically active factors enhance innate protection against infestation of macroparasites per se, especially gut parasites. The data further suggests that negative selection against enlarged salivary glands occurred as protection against electrolyte imbalances in electrolyte stressed environments and in females.

Climate↗