Prenatal Rotational Field Involving Deciduous Lateral Incisors

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66516/2/10.1177_00220345760550022501.pd

Male advancement in prenatal hand development

Male advancement in the developing hand was evidenced by 66 grossly and microscopically normal embryos in the 15–75 mm crown-rump range. Male advancement was particularly pronounced in the younger (15–30 mm) embryos, both in the proximal hand region including the round bones of the wrist and in the distal hand region, comprising the metacarpals and phalanges. Thirty-four additional embryos, abnormal in implantation or development or representing spontaneous abortion similarly evidenced male advancement in the early hand skeleton.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/37548/1/1330410302_ftp.pd

Greater female communalities in prenatal hand and dental development

As shown in 15 male and 17 female developmentally-normal, 6-9 week (15-47 mm crown-rump length) embryos, intercorrelations (communalities) involving both mesial and distal deciduous teeth and proximal and distal segments of the developing hand were systematically higher in female embryos than in male embryos, without exception, a finding in surprising accordance with postnatal dimensional and temporal development of the dentition and of the appendicular skeleton.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/22346/1/0000792.pd

Are mice good models for human neuromuscular disease? Comparing muscle excursions in walking between mice and humans

The mouse is one of the most widely used animal models to study neuromuscular diseases and test new therapeutic strategies. However, findings from successful pre-clinical studies using mouse models frequently fail to translate to humans due to various factors. Differences in muscle function between the two species could be crucial but often have been overlooked. The purpose of this study was to evaluate and compare muscle excursions in walking between mice and humans

Organ Weight Patterns in Human Fetal Development

Previous studies have reported regression formulae describing organ weight changes in often circumscribed time periods of human prenatal development. This study reports regression formulae characterizing growth in ten selected fetal organs relative to changing organ weight in 80 singleton abortuses assessed as being morphologically normal or typical-for-age, and representing weeks 13-31 (fertilization age) of pregnancy. Correlation analyses suggest that total fetal body weight or brain weight may be better reference parameters against which to assess increasing organ weights during much of the fetal period. Fetal body weight rather than the commonly used crown-rump length or menstrual age is the best reference parameter for assessing either growth of a single organ or in the generation of regression formulae. Of the ten organs monitored, the analyses of this study indicate that changes in brain weight are most highly correlated with changes in either crown-rump length or total fetal body weight. Organ weight correlations become of particular significance in the understanding of defect clusters involving organs seen in birth defect syndromes

Critical periods in the prenatal morphogenesis of the human lateral pterygoid muscle, the mandibular condyle, the articular disk, and medial articular capsule

This study was prompted by the renewed clinical interests in understanding the natural history or early morphogenesis of the human temporomandibular joint. Using histologic preparations of 52 representative human embryos and fetuses, each of the major components of the joint was systematically assessed for its changing structure and related to an approximate time scale. The emergence and continued morphogenesis of the joint articular fossa, mandibular condyle, disk, capsule, lateral pterygoid muscle fibers, and both joint cavities occur in regular temporal and spatial pattern. A key observation from this study of embryos and fetuses ranging in age from 32 days to 22 weeks is that each of the component parts of the TMJ progressively emerge with some kind of continuity from a common mass of embryonic mesenchyme interposed between the future temporal bone and mandibular regions. The observations of this study lead to the suggestion that significant development disturbances to this common tissue mass or "developmental field" can lead to anomalous morphogenesis of those structures expected to emerge over time from the "developmental field" of the temporomandibular joint. Timing and the identification of a critical time period for the joint are important variables. This study identifies the critical period in the early morphogenesis of TMJ structures as generally falling between the early 7th and 11th prenatal weeks.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26852/1/0000416.pd

Crown Area as an Indicator of Changing Crown Size in Human Pre-natal Teeth

This study deals with correlations of tooth size in human primary teeth. Traditionally, mesiodistal or buccolingual measurements have been used to express crown size. However, in this study, crown area was used as a reference parameter. Graphic reconstructions of 38 histologically prepared human fetuses with Crown-Rump Length (CRL) between 54 and 280 mm were used to obtain linear and area measurements. Based on clinical records and physical examinations, these fetuses were considered typical-for-age, or "normal". Correlation matrices indicated high levels of concordance among all developing deciduous tooth crowns and arch measurements. It was concluded that crown area is a statistically better trait to use in comparison of teeth rather than the traditional mesiodistal measurement.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66806/2/10.1177_00220345840630111001.pd