Stretching elastic tissues and using their recoil to power movement allows organisms to release energy more rapidly than by muscle contraction directly, thus amplifying power output. Chameleons employ such a mechanism to ballistically project their tongue up to two body lengths, achieving power outputs nearly three times greater than those possible via muscle contraction. Additionally, small organisms tend to be capable of greater performance than larger species performing similar movements. To test the hypothesis that small chameleon species outperform larger species during ballistic tongue projection, performance was examined during feeding among 20 chameleon species in nine genera. This revealed that small species project their tongues proportionately further than large species, achieving projection distances of 2.5 body lengths. Furthermore, feedings with peak accelerations of 2,590 m s(-2), or 264 g, and peak power output values of 14,040 W kg(-1) are reported. These values represent the highest accelerations and power outputs reported for any amniote movement, highlighting the previously underestimated performance capability of the family. These findings show that examining movements in smaller animals may expose movements harbouring cryptic power amplification mechanisms and illustrate how varying metabolic demands may help drive morphological evolution.
Considerable mechanistic data indicate there may be a sixth basic taste: fat. However, evidence demonstrating that the sensation of nonesterified fatty acids (NEFA, the proposed stimuli for “fat taste”) differs qualitatively from other tastes is lacking. Using perceptual mapping, we demonstrate that medium and long-chain NEFA have a taste sensation that is distinct from other basic tastes (sweet, sour, salty, and bitter). Although some overlap was observed between these NEFA and umami taste, this overlap is likely due to unfamiliarity with umami sensations rather than true similarity. Shorter chain fatty acids stimulate a sensation similar to sour, but as chain length increases this sensation changes. Fat taste oral signaling, and the different signals caused by different alkyl chain lengths, may hold implications for food product development, clinical practice, and public health policy.
- Proceedings of the National Academy of Sciences of the United States of America
- Published about 2 years ago
The influence of speech production on speech perception is well established in adults. However, because adults have a long history of both perceiving and producing speech, the extent to which the perception-production linkage is due to experience is unknown. We addressed this issue by asking whether articulatory configurations can influence infants' speech perception performance. To eliminate influences from specific linguistic experience, we studied preverbal, 6-mo-old infants and tested the discrimination of a nonnative, and hence never-before-experienced, speech sound distinction. In three experimental studies, we used teething toys to control the position and movement of the tongue tip while the infants listened to the speech sounds. Using ultrasound imaging technology, we verified that the teething toys consistently and effectively constrained the movement and positioning of infants' tongues. With a looking-time procedure, we found that temporarily restraining infants' articulators impeded their discrimination of a nonnative consonant contrast but only when the relevant articulator was selectively restrained to prevent the movements associated with producing those sounds. Our results provide striking evidence that even before infants speak their first words and without specific listening experience, sensorimotor information from the articulators influences speech perception. These results transform theories of speech perception by suggesting that even at the initial stages of development, oral-motor movements influence speech sound discrimination. Moreover, an experimentally induced “impairment” in articulator movement can compromise speech perception performance, raising the question of whether long-term oral-motor impairments may impact perceptual development.
Domestic cats (felis catus) have a reputation for being rather unpredictable in their dietary choices. While their appetite for protein or savory flavors is consistent with their nutritional needs, their preference among protein-sufficient dietary options may relate to differences in the response to other flavor characteristics. Studies of domestic cat taste perception are limited, in part, due to the lack of receptor sequence information. Several studies have described the phylogenetic relationship of specific cat taste receptor sequences as compared with other carnivores. For example, domestic cats are obligate carnivores and their receptor Tas1r2, associated with the human perception of sweet, is present only as a pseudogene. Similarly, the cat perception of bitter may differ from that of other mammals due to variations in their repertoire of bitter receptor (Tas2r) genes. This report includes the first functional characterization of domestic cat taste receptors.
- Proceedings of the National Academy of Sciences of the United States of America
- Published about 2 years ago
Teeth and taste buds are iteratively patterned structures that line the oro-pharynx of vertebrates. Biologists do not fully understand how teeth and taste buds develop from undifferentiated epithelium or how variation in organ density is regulated. These organs are typically studied independently because of their separate anatomical location in mammals: teeth on the jaw margin and taste buds on the tongue. However, in many aquatic animals like bony fishes, teeth and taste buds are colocalized one next to the other. Using genetic mapping in cichlid fishes, we identified shared loci controlling a positive correlation between tooth and taste bud densities. Genome intervals contained candidate genes expressed in tooth and taste bud fields. sfrp5 and bmper, notable for roles in Wingless (Wnt) and bone morphogenetic protein (BMP) signaling, were differentially expressed across cichlid species with divergent tooth and taste bud density, and were expressed in the development of both organs in mice. Synexpression analysis and chemical manipulation of Wnt, BMP, and Hedgehog (Hh) pathways suggest that a common cichlid oral lamina is competent to form teeth or taste buds. Wnt signaling couples tooth and taste bud density and BMP and Hh mediate distinct organ identity. Synthesizing data from fish and mouse, we suggest that the Wnt-BMP-Hh regulatory hierarchy that configures teeth and taste buds on mammalian jaws and tongues may be an evolutionary remnant inherited from ancestors wherein these organs were copatterned from common epithelium.
Until recently, reliable markers for adult stem cells have been lacking for many regenerative mammalian tissues. Lgr5 (leucine-rich repeat-containing G-protein coupled receptor 5) has been identified as a marker for adult stem cells in intestine, stomach, and hair follicle; Lgr5-expressing cells give rise to all types of cells in these tissues. Taste epithelium also regenerates constantly, yet the identity of adult taste stem cells remains elusive. In this study, we found that Lgr5 is strongly expressed in cells at the bottom of trench areas at the base of circumvallate and foliate taste papillae and weakly expressed in the basal area of taste buds and that Lgr5-expressing cells in posterior tongue are a subset of K14-positive epithelial cells. Lineage-tracing experiments using an inducible Cre knock-in allele in combination with Rosa26-LacZ and Rosa26-tdTomato reporter strains showed that Lgr5-expressing cells gave rise to taste cells, perigemmal cells, along with self-renewing cells at the bottom of trench areas at the base of circumvallate and foliate papillae. Moreover, using subtype-specific taste markers, we found that Lgr5-expressing cell progeny include all three major types of adult taste cells. Our results indicate that Lgr5 may mark adult taste stem or progenitor cells in the posterior portion of the tongue.
The relative risk of neurosensory deficit following removal of mandibular third molar teeth: the influence of radiography and surgical technique
- Oral surgery, oral medicine, oral pathology and oral radiology
- Published about 5 years ago
The aim of this study was to identify the relative risk of damage to the inferior dental (ID) and lingual nerves in patients undergoing lower third molar removal.
To identify factors associated with functional sensory recovery (FSR) after lingual nerve repair.
- The British journal of oral & maxillofacial surgery
- Published almost 5 years ago
Our objective was to investigate the pathway of the lingual nerve and find out whether it can be identified using ultrasonography (US) intraorally. It is a dominant sensory nerve that branches from the posterior division of the mandibular aspect of the trigeminal nerve, and is one of the two most injured nerves during oral surgery. Its anatomy in the region of the third molar has been associated with lingual nerves of variable morphology. If surgeons can identify its precise location using US, morbidity should decrease. We searched published anatomical and specialty texts, journals, and websites for reference to its site and US. Cadavers (28 nerves) were dissected to analyse its orientation at the superior lingual alveolar crest (or lingual shelf). Volunteers (140 nerves) had US scans to identify the nerve intraorally. Our search of published books and journals found that descriptions of the nerve along the superior lingual alveolar crest were inadequate. We found no US studies of the nerve in humans. Dissections showed that the nerve was above (n=6, 21%) and below (n=22, 79%) the crest of the lingual plate. US scans showed 140 lingual nerves intraorally in 70 volunteers. The nerve lay either above or below the superior lingual alveolar crest, which led us to develop a high/low classification system. US can identify the lingual nerve and help to classify it preoperatively to avoid injury. Our results suggest that clinical anatomy of the lingual nerve includes the superior lingual alveolar crest at the third and second molars because of its surgical importance. US scans can successfully identify the nerve intraorally preoperatively.
BACKGROUND: The objectives of this study were to determine the incidence of locoregional failure in patients with low-risk, early stage oral tongue squamous cell cancer (OTSCC) who undergo partial glossectomy and ipsilateral elective neck dissection without receiving postoperative radiation. METHODS: A combined database of patients with OTSCC who received treatment at Memorial Sloan-Kettering Cancer Center and Princess Margaret Cancer Center from 1985 to 2005 was established. In total, 164 patients with pathologic T1-T2N0 OTSCC who underwent partial glossectomy and ipsilateral elective neck dissection without postoperative radiation were identified. Patient-related, tumor-related, and treatment-related characteristics were recorded. Local recurrence-free survival, regional recurrence-free survival, and disease-specific survival were calculated by the Kaplan-Meier method. Predictors of outcome were analyzed by univariate and multivariate analysis. RESULTS: At a median follow-up of 66 months (range 1-171 months), the 5-year rates of local recurrence-free survival, regional recurrence-free survival, and disease-specific survival were 89%, 79.9%, and 85.6%, respectively. Regional recurrence was ipsilateral in 61% of patients and contralateral in 39% of patients. The regional recurrence rate was 5.7% for tumors <4 mm and 24% for tumors ≥4 mm. Multivariate analysis indicated that tumor thickness was the only independent predictor of neck failure (regional recurrence-free survival, 94% vs 72% [P = .02] for tumors <4 mm vs ≥4 mm, respectively). Patients who developed recurrence in the neck had a significantly poorer disease-specific survival compared with those who did not (33% vs 97%; P < .0001). CONCLUSIONS: Patients with low-risk, pathologic T1-T2N0 OTSCC had a greater than expected rate of neck failure, with contralateral recurrence accounting for close to 40% of recurrences. Failure occurred predominantly in patients who had primary tumors that were ≥4 mm thick. Cancer 2013. © 2013 American Cancer Society.