Local Monitoring Should Inform Local Solutions: Morphological Assemblages of Microplastics Are Similar within a Pathway, But Relative Total Concentrations Vary Regionally

Pathways for microplastics to aquatic ecosystems include agricultural runoff, urban runoff, and treated or untreated wastewater. To better understand the importance of each pathway as a vector for microplastics into waterbodies and for mitigation, we sampled agricultural runoff, urban stormwater runoff, treated wastewater effluent, and the waterbodies downstream in four regions across North America: the Sacramento Delta, the Mississippi River, Lake Ontario, and Chesapeake Bay. The highest concentrations of microplastics in each pathway varied by region: agricultural runoff in the Sacramento Delta and Mississippi River, urban stormwater runoff in Lake Ontario, and treated wastewater effluent in Chesapeake Bay. Material types were diverse and not unique across pathways. However, a PERMANOVA found significant differences in morphological assemblages among pathways (p < 0.005), suggesting fibers as a signature of agricultural runoff and treated wastewater effluent and rubbery fragments as a signature of stormwater. Moreover, the relationship between watershed characteristics and particle concentrations varied across watersheds (e.g., with agricultural parameters only being important in the Sacramento Delta). Overall, our results suggest that local monitoring is essential to inform effective mitigation strategies and that assessing the assemblages of morphologies should be prioritized in monitoring programs to identify important pathways of contamination.

Landscape-level variation in disease susceptibility related to shallow-water hypoxia

Diel-cycling hypoxia is widespread in shallow portions of estuaries and lagoons, especially in systems with high nutrient loads resulting from human activities. Far less is known about the effects of this form of hypoxia than deeper-water seasonal or persistent low dissolved oxygen. We examined field patterns of diel-cycling hypoxia and used field and laboratory experiments to test its effects on acquisition and progression of Perkinsus marinus infections in the eastern oyster, Crassostrea virginica, as well as on oyster growth and filtration. P. marinus infections cause the disease known as Dermo, have been responsible for declines in oyster populations, and have limited success of oyster restoration efforts. The severity of diel-cycling hypoxia varied among shallow monitored sites in Chesapeake Bay, and average daily minimum dissolved oxygen was positively correlated with average daily minimum pH. In both field and laboratory experiments, diel-cycling hypoxia increased acquisition and progression of infections, with stronger results found for younger (1-year-old) than older (2-3-year-old) oysters, and more pronounced effects on both infections and growth found in the field than in the laboratory. Filtration by oysters was reduced during brief periods of exposure to severe hypoxia. This should have reduced exposure to waterborne P. marinus, and contributed to the negative relationship found between hypoxia frequency and oyster growth. Negative effects of hypoxia on the host immune response is, therefore, the likely mechanism leading to elevated infections in oysters exposed to hypoxia relative to control treatments. Because there is considerable spatial variation in the frequency and severity of hypoxia, diel-cycling hypoxia may contribute to landscape-level spatial variation in disease dynamics within and among estuarine systems.

Sounding the alarm: studying the role of signal cascades in the immune response (EDU1P.250)

The purpose of this research opportunity was to investigate the methods and roles of cell signaling via protein cascades and their connections to the functionality of the immune system. During my summer internship, I worked with investigators at the United States Army Medical Research Institute for Infectious Diseases (USAMRIID) to develop and test the activity of man-made protease cascades that could someday mirror the complement system in its aggressive response to specific signal molecules. My research experience inspired me to develop a unit for a second year Biology/AP Biology course. Students will examine the effects of several factors, including protease concentration, substrate concentration, and a non-cascade reaction, on reaction rates through construction of both physical models and simulated protease cascades. In this unit, students first work with a hands-on physical manipulative model to familiarize them with how a protein cascade works. Then, all of the students will work in tandem on a kinesthetic activity modeling exactly how protein cascades behave. This activity allows for a cost-effective method of demonstrating protease cascades without expensive lab equipment and reagents. Students translate their knowledge into the application stage when they examine how protease cascades work in the human body and discuss various uses and effects of cascades, such as protein kinases, on the immune system.

Tibiofemoral conformity and kinematics of rotating-bearing knee prostheses

Increasing tibiofemoral articular conformity theoretically increases articular contact area and reduces contact stresses in total knee arthroplasty. Fixed-bearing knee designs possess relatively low tibiofemoral conformity, in part to allow tibiofemoral rotation without generating excessive stresses at the articulation or the implant-bone interface. This study analyzed knee kinematics of mobile-bearing designs in a closed chain dynamic knee extension model in posterior cruciate-retaining design with high- and low tibiofemoral conformity and posterior cruciate-substituting designs with and without rotational constraint. Overall, for all conditions, the mobile-bearing insert rotated with the femur in the presence of tibiofemoral axial rotation. In addition, the correlation of bearing rotation with femoral rotation was stronger for the high-conformity and rotationally-constrained designs than for the low-conformity designs and strongest for the posterior cruciate-retaining high-conformity condition. Changes in conformity or rotational constraint did not appear to affect femoral roll back, tibiofemoral axial rotation, or varus-valgus angulation. The results suggest that mobile-bearing inserts rotate with the femur and increasing conformity or rotational constraint in mobile-bearing design knee prostheses does not affect knee kinematics adversely, at least under closed chain knee extension conditions in vitro.

Comparison between the kinematics of fixed and rotating bearing knee prostheses

Rotating platform mobile bearing knee implants allow for increased tibiofemoral articular conformity without restricting axial rotation. In the current study, the effect of rotating platform knee replacement with and without posterior cruciate ligament substitution on knee kinematics was investigated. Five knees were implanted sequentially implanted with standard (fixed) bearings and then with rotating platform prostheses, each in posterior cruciate retaining and substituting designs. Three-dimensional kinematics for all knees were measured in an Oxford Knee Rig, which simulates dynamic quadriceps-driven closed kinetic chain knee extension under load. Rotating bearings did not significantly change knee kinematics when compared with fixed bearings. In this in vitro model, the cruciate retaining designs stayed more anterior, and had greater net femoral roll back and tibiofemoral valgus angulation with flexion than cruciate substituting designs.

A historical review of compartment syndrome and Volkmann's ischemic contracture

Compartment syndrome has been a recognized disease entity since the mid-nineteenth century. Extensive research and clinical observation have allowed for a better understanding of this uniquely complex disease process. Outstanding contributions by clinicians over the past century have provided the basis for our current perspective on its pathogenesis, diagnosis, and treatment. Although Volkmann's early reference to increased "pressure" as the cause of this syndrome was made over 100 years ago, today's modern concept of treatment to prevent contracture based on increased intracompartment pressure has evolved only through the combined efforts of various committed clinicians during the past century.

Clinical nursing research priorities: a Delphi study

Using the delphi technique, a group of clinical nurse specialists was surveyed regarding delineation of clinical nursing research priorities. Upon completion of the four-round survey, the results suggested that the top priorities for nursing research are: (1) factors which influence longevity in clinical nursing practice, (2) patient care delivery systems as related to nurse satisfaction, and (3) indicators of quality nursing care.