A Very General Overview of the Development Pediatric Emergency Medicine as a Specialty in the United States and Advocacy for Pediatric Healthcare; the Charge to Other Countries

One of the first noted instances regarding awareness of pediatric specific illnesses in the United States came from the writings of Dr. Benjamin Rush during the late 1700’s where he titled a section in his medical text “Diseases Specific to Children”. Throughout the 1700’s and 1800’s and even early 1900’s medicine was primarily a generalist profession where all ages were cared for by a personal family physician and there were virtually no subspecialties for adults or children.  At that time in American history children were the great neglected segment of society in families, labor, and healthcare and were often treated more as property than valued life. There were a few pediatric advocates of note. Abraham Jacobi is considered the father of modern pediatrics and advocated for pediatrics being separated from the field of obstetrics.  His actions were fundamental in the formation of the Section on Diseases of Children within the American Medical Association (AMA). In the 1930s there was a recognized need for separate pediatric specialty care advocacy organization and hence the development of the American Academy of Pediatrics (AAP) occurred. This was primarily born out of the lack of and need for federal funding to support pregnant women and children as well as the need for a foundational organization for the development of pediatrics as a specialty in the United States in the future. In the 1950’s pediatric poisonings became commonplace due to chemicals available after the end of World War II. As a result, the first poison control center was formed in Chicago and a manual was published by the AAP on pediatric poisonings. Similarly, the first cardiac surgeries for congenital heart disease were occurring and the specialty of pediatric cardiology was arising. The rising nuclear threat in the 1950’s and 1960’s also raised concern for disaster planning meeting specific pediatric needs and led to further committees, interest groups and publications. In addition, as trauma specialties and general emergency medicine grew under the auspices of the American College of Emergency Physicians (ACEP) and the American Heart Association (AHA) so did the need for sub-specialization for pediatric emergency medicine (PEM). In the early 1980s as an outgrowth of the ACEP and AAP, plans to cooperate and create the subspecialty of PEM began. The goal of the specialty was to train specialists, procure resources funding for research, and standardize training.  The first subspecialty board for PEM was administered in 1992 and has continues to this date. Another outgrowth was federally funded agency called Emergency Medicine Services for Children (EMSC) whose goal was to find and fund resources, research, and training for PEM specialists, particularly prehospital providers. As late as 2001 the Institute of Medicine in their periodic report regarding United States healthcare noted that most emergency departments were still largely deficient regarding preparedness for pediatric emergencies. Since that time there has been intense emphasis on preparedness for pediatric emergencies and now the United States has innumerable academic and community hospitals with full pediatric preparedness. Similarly, with the modern explosion of medical information it is now virtually impossible for any physician to know all of one field.  Most certainly no general emergency physician can possibly know everything regarding PEM thus obviating the need for PEM specialists to provide optimum care beyond the basics.  Numerous studies in the United States have also demonstrated seriously ill or injured children care receive superior care with better outcomes when cared for in pediatric specific facilities.  This does not imply that general emergency medicine and pediatric emergency medicine cannot co-exist and have economy of resources.  It simply seems to be true that the best possible pediatric care is delivered by pediatric subspecialists with appropriate resources, funding, facilities and training. As such it is now inconceivable that an appropriate healthcare system in the United States could exist without easily available pediatric specific resources such as PEM. Nonetheless, pediatrics continues to compete with adult specialties for resources as adults continue to have a conscious and unconscious bias toward them because of perceived greater adult patient productivity and contribution to society as a whole. In conclusion, no matter what country, there will always be a need for committed individual and organizational advocates for the specific needs of children including the firm belief in pediatric subspecialties such as pediatric emergency medicine

Ontogenetic Scaling of the Olfactory Antennae and Flicking Behavior of the Shore Crab, \u3cem\u3eHemigrapsus oregonensis\u3c/em\u3e

Malacostracan crustaceans such as crabs flick antennae with arrays of olfactory sensilla called aesthetascs through the water to sense odors. Flicking by crabs consists of a quick downstroke, in which aesthetascs are deflected laterally (splayed), and a slower, reversed return stroke, in which aesthetascs clump together. This motion causes water to be flushed within and then held in between aesthetascs to deliver odor molecules to olfactory receptors. Although this odor sampling method relies on a narrow range of speeds, sizes, and specific arrangements of aesthetascs, most crabs dramatically change these during ontogeny. In this study, the morphometrics of the aesthetascs, array, and antennae and the flicking kinematics of the Oregon shore crab, Hemigrapsus oregonensis (Decapoda: Brachyura), are examined to determine their scaling relationships during ontogeny. The morphometrics of the array and antennae increase more slowly than would be predicted by isometry. Juvenile crabs’ aesthetascs splay relatively further apart than adults, likely due to changing material properties of aesthetasc cuticle during growth. These results suggest that disproportionate growth and altered aesthetasc splay during flicking will mediate the size changes due to growth that would otherwise lead to a loss of function

The Role of the Pericardium in the Valveless, Tubular Heart of the Tunicate, \u3cem\u3eCiona savignyi\u3c/em\u3e

Tunicates, small invertebrates within the phylum Chordata, possess a robust tubular heart which pumps blood through their open circulatory systems without the use of valves. This heart consists of two major components: the tubular myocardium, a flexible layer of myocardial cells that actively contracts to drive fluid down the length of the tube; and the pericardium, a stiff, outer layer of cells that surrounds the myocardium and creates a fluid-filled space between the myocardium and the pericardium. We investigated the role of the pericardium through in vivo manipulations on tunicate hearts and computational simulations of the myocardium and pericardium using the immersed boundary method. Experimental manipulations reveal that damage to the pericardium results in aneurysm-like bulging of the myocardium and major reductions in the net blood flow and percentage closure of the heart\u27s lumen during contraction. In addition, varying the pericardium-to-myocardium (PM) diameter ratio by increasing damage severity was positively correlated with peak dye flow in the heart. Computational simulations mirror the results of varying the PM ratio experimentally. Reducing the stiffness of the myocardium in the simulations reduced mean blood flow only for simulations without a pericardium. These results indicate that the pericardium has the ability to functionally increase the stiffness of the myocardium and limit myocardial aneurysms. The pericardium\u27s function is likely to enhance flow through the highly resistive circulatory system by acting as a support structure in the absence of connective tissue within the myocardium

Large Amplitude, Short Wave Peristalsis and Its Implications for Transport

Valveless, tubular pumps are widespread in the animal kingdom, but the mechanism by which these pumps generate fluid flow is often in dispute. Where the pumping mechanism of many organs was once described as peristalsis, other mechanisms, such as dynamic suction pumping, have been suggested as possible alternative mechanisms. Peristalsis is often evaluated using criteria established in a technical definition for mechanical pumps, but this definition is based on a small-amplitude, long-wave approximation which biological pumps often violate. In this study, we use a direct numerical simulation of large-amplitude, short-wave peristalsis to investigate the relationships between fluid flow, compression frequency, compression wave speed, and tube occlusion. We also explore how the flows produced differ from the criteria outlined in the technical definition of peristalsis. We find that many of the technical criteria are violated by our model: Fluid flow speeds produced by peristalsis are greater than the speeds of the compression wave; fluid flow is pulsatile; and flow speed have a nonlinear relationship with compression frequency when compression wave speed is held constant. We suggest that the technical definition is inappropriate for evaluating peristalsis as a pumping mechanism for biological pumps because they too frequently violate the assumptions inherent in these criteria. Instead, we recommend that a simpler, more inclusive definition be used for assessing peristalsis as a pumping mechanism based on the presence of non-stationary compression sites that propagate unidirectionally along a tube without the need for a structurally fixed flow direction

What Can Computational Modeling Tell Us About the Diversity of Odor-Capture Structures in the Pancrustacea?

A major transition in the history of the Pancrustacea was the invasion of several lineages of these animals onto land. We investigated the functional performance of odor-capture organs, antennae with olfactory sensilla arrays, through the use of a computational model of advection and diffusion of odorants to olfactory sensilla while varying three parameters thought to be important to odor capture (Reynolds number, gap-width-to-sensillum-diameter ratio, and angle of the sensilla array with respect to oncoming flow). We also performed a sensitivity analysis on these parameters using uncertainty quantification to analyze their relative contributions to odor-capture performance. The results of this analysis indicate that odor capture in water and in air are fundamentally different. Odor capture in water and leakiness of the array are highly sensitive to Reynolds number and moderately sensitive to angle, whereas odor capture in air is highly sensitive to gap widths between sensilla and moderately sensitive to angle. Leakiness is not a good predictor of odor capture in air, likely due to the relative importance of diffusion to odor transport in air compared to water. We also used the sensitivity analysis to make predictions about morphological and kinematic diversity in extant groups of aquatic and terrestrial crustaceans. Aquatic crustaceans will likely exhibit denser arrays and induce flow within the arrays, whereas terrestrial crustaceans will rely on more sparse arrays with wider gaps and little-to-no animal-induced currents

A Tale of Two Antennules: The Performance of Crab Odor-Capture Organs in Air and Water

Odour capture is an important part of olfaction, where dissolved chemical cues (odours) are brought into contact with chemosensory structures. Antennule flicking by marine crabs is an example of discrete odour capture (sniffing) where an array of chemosensory hairs is waved through the water to create a flow–no flow pattern based on a narrow range of speeds, diameters of and spacings between hairs. Changing the speed of movement and spacing of hairs at this scale to manipulate flow represents a complicated fluid dynamics problem. In this study, we use numerical simulation of the advection and diffusion of a chemical gradient to reveal how morphological differences of the hair arrays affect odour capture. Specifically, we simulate odour capture by a marine crab (Callinectes sapidus) and a terrestrial crab (Coenobita rugosus) in both air and water to compare performance. We find that the antennule morphologies of each species are adaptions to capturing odours in their native habitats. Sniffing is an important part of odour capture for marine crabs in water where the diffusivity of odorant molecules is low and flow through the array is necessary. On the other hand, flow within the hair array diminishes odour-capture performance in air where diffusivities are high. This study highlights some of the adaptations necessary to transition from water to air

Modeling Action Potential Reversals in Tunicate Hearts

Tunicates are small invertebrates which possess a unique ability to reverse flow in their hearts. Scientists have debated various theories regarding how and why flow reversals occur. Here we explore the electrophysiological basis for reversals by simulating action potential propagation in an idealized model of the tubelike tunicate heart. Using asymptotic formulas for action potential duration and conduction velocity, we propose tunicate-specific parameters for a two-current ionic model of the action potential. Then, using a kinematic model, we derive analytical criteria for reversals to occur. These criteria inform subsequent numerical simulations of action potential propagation in a fiber paced at both ends. In particular, we explore the role that variability of pacemaker firing rates plays in generating reversals, and we identify various favorable conditions for triggering retrograde propagation. Our analytical framework extends to other species; for instance, it can be used to model competition between the sinoatrial node and abnormal ectopic foci in human heart tissue

The Fire-Oak Literature of Eastern North America: Synthesis and Guidelines

Guidelines for using prescribed fire to regenerate and restore upland oak forests, woodlands, and savannas in eastern North America were developed by synthesizing the results of more than 100 scientific publications. The first four chapters provide background information on the values of oak ecosystems, eastern fire history, oak’s adaptations to fire, and the findings of fire-oak research conducted over the past 50 years. The final chapter synthesizes that background information into guidelines that explain how to use prescribed fire to facilitate oak seedling establishment, release oak reproduction from competing mesophytic hardwoods, and rehabilitate open oak woodlands, oak savannas, and scrub oak communities. A reference section is also provided for readers desiring to delve more deeply into the associations between periodic fire and oak forests, woodlands, and savannas

Scaling of Olfactory Antennae of the Terrestrial Hermit Crabs \u3cem\u3eCoenobita rugosus\u3c/em\u3e and \u3cem\u3eCoenobita perlatus\u3c/em\u3e During Ontogeny

Although many lineages of terrestrial crustaceans have poor olfactory capabilities, crabs in the family Coenobitidae, including the terrestrial hermit crabs in the genus Coenobita, are able to locate food and water using olfactory antennae (antennules) to capture odors from the surrounding air. Terrestrial hermit crabs begin their lives as small marine larvae and must find a suitable place to undergo metamorphosis into a juvenile form, which initiates their transition to land. Juveniles increase in size by more than an order of magnitude to reach adult size. Since odor capture is a process heavily dependent on the size and speed of the antennules and physical properties of the fluid, both the transition from water to air and the large increase in size during ontogeny could impact odor capture. In this study, we examine two species of terrestrial hermit crabs, Coenobita perlatus H. Milne-Edwards and Coenobita rugosus H. Milne-Edwards, to determine how the antennule morphometrics and kinematics of flicking change in comparison to body size during ontogeny, and how this scaling relationship could impact odor capture by using a simple model of mass transport in flow. Many features of the antennules, including the chemosensory sensilla, scaled allometrically with carapace width and increased slower than expected by isometry, resulting in relatively larger antennules on juvenile animals. Flicking speed scaled as expected with isometry. Our mass-transport model showed that allometric scaling of antennule morphometrics and kinematics leads to thinner boundary layers of attached fluid around the antennule during flicking and higher odorant capture rates as compared to antennules which scaled isometrically. There were no significant differences in morphometric or kinematic measurements between the two species

Flexibility of Crab Chemosensory Hairs Enables Flicking Antennules to Sniff

The first step in smelling is capture of odorant molecules from the surrounding fluid. We used lateral flagella of olfactory antennules of crabs Callinectes sapidus to study the physical process of odor capture by antennae bearing dense tufts of hair-like chemosensory sensilla (aesthetascs). Fluid flow around and through aesthetasc arrays on dynamically scaled models of lateral flagella of C. sapidus was measured by particle image velocimetry to determine how antennules sample the surrounding water when they flick. Models enabled separate evaluation of the effects of flicking speed, aesthetasc spacing, and antennule orientation. We found that crab antennules, like those of other malacostracan crustaceans, take a discrete water sample during each flick by having a rapid downstroke, during which water flows into the aesthetasc array, and a slow recovery stroke, when water is trapped in the array and odorants have time to diffuse to aesthetascs. However, unlike antennules of crustaceans with sparse aesthetasc arrays, crabs enhance sniffing via additional mechanisms: 1) Aesthetascs are flexible and splay as a result of the hydrodynamic drag during downstrokes, then clump together during return strokes; and 2) antennules flick with aesthetascs on the upstream side of the stalk during downstrokes, but are hidden downstream during return strokes. Aiming aesthetascs into ambient flow maintains sniffing. When gaps between aesthetascs are wide, changes in antennule speed are more effective at altering flow through the array than when gaps are narrow. Nonetheless, if crabs had fixed gap widths, their ability to take discrete samples of their odorant environment would be diminished