Leaf teeth, transpiration and the retrieval of apoplastic solutes in balsam poplar

The rapid flow of the transpiration stream through major veins to leaf teeth was followed in leaves of Populus balsamifera L., using the tracer sulphorhodamine G (SR), which probes for cells with H⁺-extrusion pumps. The tracer accumulated quickly in the hydathodes of the teeth. It was shown by freeze-substitution and anhydrous processing that SR was taken up by phloem parenchyma and epithem cells of the hydathode. When ¹⁴C-labelled aspartate was fed to the leaves in the transpiration stream, it also was taken up most strongly by the same phloem parenchyma and epithem cells. It is proposed that one function of the hydathodes in leaf teeth is the retrieval of solutes from the transpiration stream.     

Trace-element analysis of human teeth and bone by proton-induced X-ray emission

The objective of our study is to correlate Fe, Cu, Zn, Pb, Br, Sr, and Mo concentrations in human teeth crown, root, and bone. The samples, teeth from a lower jaw bone and the lower jaw bone itself, were obtained from a 97-yr-old female cadaver. Two hundred milligrams of crown and root of the teeth, and lower jaw bones were fixed to a Kapton film and irradiated with a 3.8-MeV external proton beam from an 8-MV FN Tandem Van de Graaff Accelerator. TheF-test was used to analyze the difference between crown, root, and bone. It resulted in the following: For Fe, Zn, and Pb, the comparison showed significant differences among the three sample populations of tooth crown, root, and bone; for Cu, Br, Sr, and Mo, the comparison showed no significant differences among all three sample populations. Several elements in the samples were highly interrelated.     

两广部分地区猩猩化石的研究

本文对广东罗定、云浮及广西等地的猩猩牙齿化石进行了宏观及微观的形态观察。认为猩猩牙齿咬合面除有较多的褶皱外,大多数标本上还有明显的生长线。化石猩猩牙齿与现生种的相比.牙齿的生长线后者不如前者显著;牙齿的大小是后者小于前者。这些现象表明Hooijer(1948)提出的 Pongo Pygmaeus weidenreichi可以成立。     

Tooth wear in Australian aboriginal populations from the River Murray Valley

The study of tooth wear among prehistoric and recent populations has frequently been concerned with the rate and pattern of wear over the dental arches. In this report we considered the question of tooth wear variation among collections of Australian Aboriginal crania recovered from several sites along the Murray River in Southeastern Australia. These crania represent the remains of relatively recent populations from about 2,000 years ago until the early 19th century. The degree of tooth wear for each dental arch was recorded by an established method of determining the ratio of exposed dentin. The pattern or distribution of wear over each arch was summarized by principal component analysis. The mean wear degree and pattern were compared among four geographical grouping of crania separated by up to 700 miles of river frontage. Our results showed, as expected, a significant difference between the well-defined population at the Lower Murray site (Swanport) and the three upriver groups. However, there were significant differences among these three collections as well. Sexual dimorphism was noted but was only significant in the Lower Murray group; the mean wear was greater and also more variable among the males. At the second of the Middle Murray sites the pattern of wear was different and the degree of wear was significantly less than in the other groups. A possible explanation for this diversity may be environmental and subsistence base differences. The evidence from the Lower Murray supports this possibility, but the differences among the other three groups are not as clearly established. However, our results do suggest that the Murray Black collection, from which these crania were obtained, may not be as homogeneous a group as previously believed.     

The presence of a side population and its marker ABCG2 in human deciduous dental pulp cells

Stem cells have been identified using the DNA-binding dye Hoechst 33342 and flow cytometry (FCM) in various tissues known as the side population (SP). The present study shows, for the first time, the presence of side population cells in human deciduous dental pulp cells (DPCs). Flow cytometric identification revealed that 2% of human deciduous DPCs were SP cells and that this SP profile disappeared in the presence of verapamil. The SP marker ABCG2 protein was localized to DPCs in the cell membrane by immunofluorescence staining, and flow cytometric analysis demonstrated that 3.6% of DPCs were ABCG2-positive. Furthermore, quantitative real-time PCR proved that ABCG2 mRNA expression in DPCs isolated from human exfoliated deciduous teeth was higher than in DPCs from permanent teeth. Our findings demonstrate that DPCs from human exfoliated deciduous teeth contain a higher proportion of the SP phenotype than permanent teeth and that they may constitute a stem cell population.     

Long noncoding RNA C21orf121/bone morphogenetic protein 2/microRNA-140-5p gene network promotes directed differentiation of stem cells from human exfoliated deciduous teeth to neuronal cells

Previous studies have revealed that long noncoding RNA (lncRNA) and microRNA play a crucial role in autism, which is a childhood neurodevelopmental disorder with complicated genetic origins. Hence, the study concerns whether lncRNA C21orf121/bone morphogenetic proteins 2 (BMP2)/miR-140-5p gene network affects directed differentiation of stem cells from human exfoliated deciduous teeth (SHED) to neuronal cells in rats with autism. Autism models were successfully established. The neuron cells that differentiated from SHED cell were identified. The expression of lncRNA C21orf121, miR-140-5p, BMP2, Nestin, βIII-tubulin, and microtubule-associated protein 2 (MAP2) and the expression of neuron-specific enolase (NSE) were examined. Besides, the gap junction (GJ) function of SHED, the intracellular free Ca ²⁺ concentration, and the social behavior and repetitive stereotyped movements of rats in autism were detected. The target relationship between lncRNA C21orf121 and miR-140-5p and that between miR-140-5p and BMP2 were also verified. Firstly, we successfully isolated SHED and identified the differentiated neurons of SHED. Besides, the expression of BMP2, MAP2, Nestin, βIII-tubulin, NSE positive rate, GJ function, and intracellular free Ca ²⁺ concentration were increased with the upregulation of C21orf121 and downregulation of miR-140-5p, and accumulated time of repetitive stereotyped movements decreased and the frequency of social behavior increased. The results indicate that lncRNA C21orf121 as a competing endogenous RNA competes with BMP2 binding to miR-140-5p, thereby promoting SHED to differentiate into neuronal cells via upregulating BMP2 expression.     

Early development and replacement of the stickleback dentition

Teeth have long served as a model system to study basic questions about vertebrate organogenesis, morphogenesis, and evolution. In nonmammalian vertebrates, teeth typically regenerate throughout adult life. Fish have evolved a tremendous diversity in dental patterning in both their oral and pharyngeal dentitions, offering numerous opportunities to study how morphology develops, regenerates, and evolves in different lineages. Threespine stickleback fish (Gasterosteus aculeatus) have emerged as a new system to study how morphology evolves, and provide a particularly powerful system to study the development and evolution of dental morphology. Here, we describe the oral and pharyngeal dentitions of stickleback fish, providing additional morphological, histological, and molecular evidence for homology of oral and pharyngeal teeth. Focusing on the ventral pharyngeal dentition in a dense developmental time course of lab‐reared fish, we describe the temporal and spatial consensus sequence of early tooth formation. Early in development, this sequence is highly stereotypical and consists of seventeen primary teeth forming the early tooth field, followed by the first tooth replacement event. Comparing this detailed morphological and ontogenetic sequence to that described in other fish reveals that major changes to how dental morphology arises and regenerates have evolved across different fish lineages. J. Morphol. 277:1072–1083, 2016. © 2016 Wiley Periodicals, Inc.     

Mandibular movement patterns relative to food types in common tree shrews (Tupaia glis)

Although common tree shrews have long been considered a model system for early eutherian mastication, little information on mandibular movement patterns relative to specific food types has been reported. Detailed analysis of mandibular movement patterns when related to resulting attrition facets may permit more accurate extrapolations regarding the dietary habits of primitive mammals. Marker beads were sewn to chins of five animals that were placed in a restraint system and filmed while they fully masticated mealworm larvae and standardized pieces of banana, almond, and commercial cat chow. These sequences were divided into early, middle, and late thirds of food reduction. Mandibular positions from both frontal and lateral perspectives were digitized frame by frame to yield plots of orbits in three dimensions as well as graphic display of displacements, velocities, and accelerations. Plot coordinates were averaged to generate composite orbital shapes. Significant (p < 0.01) findings included: (1) shortest orbital durations and greatest peak closing velocities and accelerations in early third of reduction; (2) smallest maximum gape, smallest maximum lateral excursion from midline, and longest duration of powerstroke relative to orbital duration in late third of reduction; (3) shortest orbital durations and smallest maximum gape during mastication of chow; (4) greatest maximum lateral excursion during mastication of mealworm larvae; and (5) smallest peak closing accelerations during mastication of banana. Significant differences were also found among subjects for all parameters examined. Capacity for complex jaw movement may have been critical for allowing primitive molars to be used for trituration of a variety of food types, and may have preceded evolution of more specialized molar forms.