The gross anatomy of the mouth of snakes has always been interpreted as an evolutionary response to feeding demands. In most alethinophidian species, their anatomy allows limited functional independence of right and left sides and the roof and floor of the mouth as well as wide separation of the tips of the mandibles. However, locations of the tongue and glottis in snakes suggest extraordinary rearrangement of pharyngeal structures characteristic of all vertebrates. Serial histological sections through the heads of a number of colubroid species show muscularis mucosal smooth muscle fibers appearing in the paratracheal gutter of the lower jaw at varying levels between the eye and ear regions. Incomplete muscularis externa elements appear beneath the paratracheal gutter more caudally but typically at otic levels. Both muscle layers encompass more of the gut wall at more posterior levels, encircling the gut at the level of the atlas or axis. The pattern in snakes suggests developmental dissociation of dorsal and ventral splanchnic derivatives and extensive topological rearrangements of some ventral pharyngeal arch derivatives typical of most tetrapods. When snakes swallow large prey, the effective oral cavity becomes extremely short ventrally. The palatomaxillary arches function as ratchets packing the prey almost directly into the esophagus. Our findings raise questions about germ layer origins and regulation of differentiation of gut regions and derivatives in snakes and suggest that significant aspects of the evolution of lepidosaurs may be difficult to recover from bones or molecular sequence data alone. Anat Rec,

Background:Calsequestrin is essential to keep a high calcium concentration inside the sarcoplasmic reticulum of muscle fibers. Results: In situ, calsequestrin polymers appear to form a three-dimensional structure with repeated nodal points. Conclusion: A three-dimensional calsequestrin polymer matrix is very suitable for its spatially confined calcium storage function. Significance: The calsequestrin structure has been extensively studied in ex vivo systems. This approach illustrates the behavior of the protein while still in its physiological cell localization.

The skin of squamates consists of a keratinized epidermis divided into thick scale and thinner, folded interscale regions underlain by a dermis containing a complex array of fibrous connective tissues. We examined the skin of the lower jaw of watersnakes (Nerodia sipedon) to determine how skin morphology changes when highly stretched during ingestion of large prey. Video records of skin behavior in the lower jaws of watersnakes feeding on fish or anesthetized watersnakes being stretched on an Instron machine showed that most skin extension involves the interscale skin. The largest intermandibular separation recorded during feeding was 7.7× resting distance, but intermandibular separation reached 10× without tissue failure during mechanical testing. Histological and anatomical analyses of lower jaws fixed in resting, moderately or highly stretched conditions showed that stretching had little effect on scale regions of the epidermis. However, stretching flattened folds of interscale regions at both gross and cellular levels and imposed changes in epidermal cell shape. Stretching of the dermis is primarily limited to realignment of collagen and stretching of elastin in the deep dermis. The configuration of dermal elastin suggests a model for passive recovery of epidermal folding following release of tension.

Braiding may place the collagen fibers in a suboptimal orientation for loading that results in a weaker graft. We do not recommend the use of braiding if the strongest, stiffest initial graft is desired.

Most mammals have deformable bodies, making it difficult to measure the size of living or freshly killed ones accurately. Because small rodents are common prey of many snakes, and because nearly all snakes swallow their prey whole, we explored four methods for determining the ingestible size (the smallest cross-sectional area that the largest part of the rodent can be made into without breaking bones or dislocating joints) of 100 intact rodents, including 50 Musmusculus and 50 Rattus norvegicus. Cross-sectional areas derived from maximal height and width of specimens at rest or the same specimens wrapped snout to pelvic girdle are roughly 1.5× higher than areas calculated either by the height and width of the same specimens rolled into cylinders or by volumetric displacement. Rolling rodents into cylinders reduces cross-sectional area by straightening the vertebral column, lengthening the abdominal cavity, elevating the sternum, compressing the thoracic cavity, and protracting the shoulder joint, that is, changes similar to those seen in rodents eaten by snakes. Reduced major axis regression of the smallest attainable cross-sectional area, y, on mass, x, shows that y (in log mm(2) ) approximates 1.53x (in log grams)(0.69) for rats and 1.63x(0.64) for mice. Our results suggest that visual cues provided by live rodents might lead most predators, like snakes, to overestimate ingestible size and hence rarely attack prey too large to ingest.

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Many snakes swallow large prey whole, and this process requires large displacements of the unfused tips of the mandibles and passive stretching of the soft tissues connecting them. Under these conditions, the intermandibular muscles are highly stretched but subsequently recover normal function. In the highly stretched condition we observed in snakes, sarcomere length (SL) increased 210% its resting value (SL 0 ), and actin and myosin filaments no longer overlapped. Myofibrils fell out of register and triad alignment was disrupted. Following passive recovery, SLs returned to 82% SL 0 , creating a region of double-overlapping actin filaments. Recovery required recoil of intracellular titin filaments, elastic cytoskeletal components for realigning myofibrils, and muscle activation. Stretch of whole muscles exceeded that of sarcomeres as a result of extension of folded terminal tendon fibrils, stretching of extracellular elastin and independent slippage of muscle fibers. Snake intermandibular muscles thus provide a unique model of how basic components of vertebrate skeletal muscle can be modified to permit extreme extensibility.

Obesity among children is rising at an alarming rate. This study examines pediatric emergency department visits for children aged 2 to 17 years to determine the prevalence of normal, overweight, and obesity as well as to characterize discharge diagnosis and level of service among the different groups. The electronic emergency department medical record and billing service data were used in the review process. Body mass index (BMI) and percentiles were calculated using the Centers for Disease Control formulas with overweight being defined as BMI between 85th and 94th sex- and age-specific percentiles and obesity as greater than 95th sex- and age-specific percentile. The study was reviewed and approved by the institutional review board. Of the 596 patients meeting inclusion criteria, there was a predominance of African American and Hispanic patients. Approximately 53% (313) of patients were classified as normal weight, while 46% (272) of patients were either overweight or obese. The percentages of overweight and obesity were similar across racial/ethnic classifications, with a slight predominance of obesity among minority groups (30% and 35%, respectively, in minority groups vs 28% and 25%, respectively, in nonminority groups). There were no statistically significant differences between discharge diagnosis and level of service among the different weight categories. Rates of overweight and obesity in this predominately minority pediatric population were significantly greater than the published national rates. The impact of the epidemic of childhood obesity mandates the need for innovative strategies of weight control and reduction. Emergency departments routinely treat high-risk pediatric populations and can therefore serve as a resource for screening and early referral that has been previously untapped in combating childhood obesity.