Characterization of the shoulder net joint moment during manual wheelchair propulsion using four functional axes.

Understanding how individuals distribute mechanical demand imposed on their upper extremity during physically demanding activities provides meaningful insights to preserve function and mitigate detrimental mechanical loading of the shoulder. In this study, we hypothesized that parameterization of the shoulder net joint moment using four functional axes could characterize distribution tendencies about the shoulder during manual wheelchair propulsion and that regardless of demographics, a shoulder flexor dominant NJM distribution would be predominantly used by individuals with paraplegia (n = 130). Forces and kinematics of the upper extremity and trunk were quantified using motion capture and an instrumented wheel during steady state manual wheelchair propulsion at self-selected fast speeds on a stationary ergometer. The results indicate that parsing out the internal/external rotation component of the shoulder net joint moment about the upper arm and distributing the remainder across the three orthogonal axes of the torso was successful in identifying common shoulder net joint moment distribution techniques used across individuals with paraplegia during manual wheelchair propulsion. Distribution tendencies were predominantly flexor dominant across injury level, gender, time since injury, body mass index, and height demographics. The 4-axis parameterization of the shoulder NJM effectively differentiated moment distribution tendencies used by individuals during manual wheelchair propulsion using a functionally relevant representation of shoulder kinetics. Use of the four-axis parameterization of joint kinetics in future studies is expected to provide important insights that can advance knowledge, preserve function, and inform clinical decisions.

Hemocytic sarcoma of the body wall in a California king crab Paralithodes californiensis.

Neoplasia is rarely reported in decapod crustaceans, and sarcoma has not been previously reported in any crab species. A California king crab Paralithodes californiensis with a recent history of autotomy (4 legs lost) and anorexia was found dead. Grossly, the crab had a pigmented ulcer on the right cheliped merus. Necropsy tissue samples were placed in 10% neutral buffered formalin and processed routinely for histology. Both histochemical (i.e. Brown and Brenn Gram, Fite-Faraco acid fast, Fontana-Masson, Giemsa, hematoxylin and eosin, Masson's trichrome, periodic acid-Schiff [PAS], phosphotungstic acid-hematoxylin, and von Kossa) and immunohistochemical (i.e. cytokeratin, vimentin, and lysozyme) stains were performed. The body wall (presumably of the right cheliped merus) was ulcerated and subtended by a densely cellular, unencapsulated, invasive neoplasm composed of spindle cells arranged in intersecting streams and bundles embedded in a small to moderate amount of fibromatous stroma. Neoplastic cells were oval to elongate with fibrillar, pale eosinophilic cytoplasm that occasionally contained moderate numbers of small, spherical, brightly eosinophilic granules that were highlighted with PAS and Giemsa stains. Neoplastic cells had mild atypia and no evident mitoses. Immunohistochemical stains were noncontributory. This neoplasm is consistent with hemocytic sarcoma of semi-granulocytic origin. Decapod crustaceans have 3 types of hemocytes: hyalinocytes, granulocytes, and semi-granulocytes. Neoplastic cells had PAS- and Giemsa-positive granules, which are present in both semi-granulocytes and granulocytes. Semi-granulocytes can elongate and are associated with deposition of extracellular matrix during some immune responses. Neoplastic cells were elongate and associated with deposition of matrix. These findings suggest neoplastic cells were of semi-granulocytic origin.

Regulation of reaction forces during the golf swing.

During the golf swing, the reaction forces applied at the feet control translation and rotation of the body-club system. In this study, we hypothesized that skilled players using a 6-iron would regulate shot distance by scaling the magnitude of the resultant horizontal reaction force applied to the each foot with minimal modifications in force direction. Skilled players (n = 12) hit golf balls using a 6-iron. Shot distance was varied by hitting the ball as they would normally and when reducing shot distance using the same club. During each swing, reaction forces were measured using dual force plates (1200 Hz) and three-dimensional kinematics were simultaneously captured (110 Hz). The results indicate that, on average, the peak resultant horizontal reaction forces of the target leg were significantly less than normal (5%, p < 0.05) when reducing shot distance. No significant differences in the orientation of the peak resultant horizontal reaction forces were observed. Resultant horizontal reaction force-angle relationships within leg and temporal relationships between target and rear legs during the swing were consistent within player across shot conditions. Regulation of force magnitude with minimal modification in force direction is expected to provide advantages from muscle activation, coordination, and performance points of view.

Bioassay of estrogenicity and chemical analyses of estrogens in streams across the United States associated with livestock operations.

Animal manures, used as a nitrogen source for crop production, are often associated with negative impacts on nutrient levels in surface water. The concentrations of estrogens in streams from these manures also are of concern due to potential endocrine disruption in aquatic species. Streams associated with livestock operations were sampled by discrete samples (n = 38) or by time-integrated polar organic chemical integrative samplers (POCIS, n = 19). Samples were analyzed for estrogens by gas chromatography-tandem mass spectrometry (GC-MS(2)) and estrogenic activity was assessed by three bioassays: Yeast Estrogen Screen (YES), T47D-KBluc Assay, MCF-7 Estrogenicity Screen (E-Screen). Samples were collected from 19 streams within small (≈ 1-30 km(2)) watersheds in 12 U.S. states representing a range of hydrogeologic conditions, dominated by: dairy (3), grazing beef (3), feedlot cattle (1); swine (5); poultry (3); and 4 areas where no livestock were raised or manure was applied. Water samples were consistently below the United Kingdom proposed Lowest Observable Effect Concentration for 17ß-estradiol in fish (10 ng/L) in all watersheds, regardless of land use. Estrogenic activity was often higher in samples during runoff conditions following a period of manure application. Estrone was the most commonly detected estrogen (13 of 38 water samples, mean 1.9, maximum 8.3 ng/L). Because of the T47D-KBluc assay's sensitivity towards estrone (1.4 times 17ß-estradiol) it was the most sensitive method for detecting estrogens, followed by the E-Screen, GC-MS(2), and YES. POCIS resulted in more frequent detections of estrogens than discrete water samples across all sites, even when applying the less-sensitive YES bioassay to the POCIS extracts.

Thinning of large mammalian cells for cryo-TEM characterization by cryo-FIB milling.

Focused ion beam milling at cryogenic temperatures (cryo-FIB) is a valuable tool that can be used to thin vitreous biological specimens for subsequent imaging and analysis by cryo-transmission electron microscopy (cryo-TEM) in a frozen-hydrated state. This technique offers the potential benefit of eliminating the mechanical artefacts that are typically found with cryo-ultramicrotomy. However, due to the additional complexity in transferring samples in and out of the FIB, contamination and devitrification of the amorphous ice is commonly encountered. To address these problems, we have designed a sample cryo-shuttle that directly and specifically accepts Polara TEM cartridges to simplify the transfer process between FIB and TEM. We optimized several parameters in the cryo-FIB and cryo-TEM processes using the quality of the samples' ice as an indicator and demonstrated high-quality milling with large mammalian cells. By comparing the results from HeLa cells to those from Escherichia coli cells, we discuss some of the artefacts and challenges we have encountered using this technique.

Combined sewer overflows: an environmental source of hormones and wastewater micropollutants.

Data were collected at a wastewater treatment plant (WWTP) in Burlington, Vermont, USA, (serving 30,000 people) to assess the relative contribution of CSO (combined sewer overflow) bypass flows and treated wastewater effluent to the load of steroid hormones and other wastewater micropollutants (WMPs) from a WWTP to a lake. Flow-weighted composite samples were collected over a 13 month period at this WWTP from CSO bypass flows or plant influent flows (n = 28) and treated effluent discharges (n = 22). Although CSO discharges represent 10% of the total annual water discharge (CSO plus treated plant effluent discharges) from the WWTP, CSO discharges contribute 40-90% of the annual load for hormones and WMPs with high (>90%) wastewater treatment removal efficiency. By contrast, compounds with low removal efficiencies (<90%) have less than 10% of annual load contributed by CSO discharges. Concentrations of estrogens, androgens, and WMPs generally are 10 times higher in CSO discharges compared to treated wastewater discharges. Compound concentrations in samples of CSO discharges generally decrease with increasing flow because of wastewater dilution by rainfall runoff. By contrast, concentrations of hormones and many WMPs in samples from treated discharges can increase with increasing flow due to decreasing removal efficiency.

Multijoint control strategies transfer between tasks.

In this paper, the hypothesis that multijoint control strategies are transferred between similar tasks was tested. To test this hypothesis, we studied the take-off phase of two types of backward somersault dives: one while translating backwards (Back), the other while translating forward (Reverse). An experimentally based dynamic model of the musculoskeletal system was employed to simulate the measured kinematics and reaction force data and to study the sensitivity of take-off performance to initial kinematic conditions. It was found that the horizontal velocity of the total body center of mass (CM) was most sensitive to modifications in the initial shank conditions. Consequently, the initial shank kinematics of the Back dive was modified in the optimization procedure while maintaining the joint coordination of the Back in order to generate the CM trajectory and reaction forces of a Reverse. Similarly, the initial shank kinematics of the Reverse dive was modified to simulate the CM trajectory and reaction force of the Back. It was found that small modifications in the initial shank kinematics led to change in direction of horizontal CM velocity at take-off; resulting in a switch from Back to Reverse and vice versa. In both cases, the simulated momentum conditions at departure and the bimodal shape of the reaction force-time curve were consistent with those experimentally observed. The results of this study support the hypothesis that transfer of control strategies between similar tasks is a viable option in multijoint control. This transfer of control strategy is explained using a hierarchical model of the motion control system.

Lower extremity control and dynamics during backward angular impulse generation in forward translating tasks.

Observation of complex whole body movements suggests that the nervous system coordinates multiple operational subsystems using some type of hierarchical control. When comparing two forward translating tasks performed with and without backward angular impulse, we have learned that both trunk-leg coordination and reaction force-time characteristics are significantly different between tasks. This led us to hypothesize that differences in trunk-leg coordination and reaction force generation would induce between-task differences in the control of the lower extremity joints during impulse generation phase of the tasks. Eight highly skilled performers executed a series of forward jumps with and without backward rotation (reverse somersault and reverse timer, respectively). Sagittal plane kinematics, reaction forces, and electromyograms of lower extremity muscles were acquired during the take-off phase of both tasks. Lower extremity joint kinetics were calculated using inverse dynamics. The results demonstrated between-task differences in the relative angles between the lower extremity segments and the net joint forces/reaction force and the joint angular velocity profiles. Significantly less knee extensor net joint moments and net joint moment work and greater hip extensor net joint moments and net joint moment work were observed during the push interval of the reverse somersault as compared to the reverse timer. Between-task differences in lower extremity joint kinetics were regulated by selectively activating the bi-articular muscles crossing the knee and hip. These results indicate that between-task differences in the control of the center of mass relative to the reaction force alters control and dynamics of the multijoint lower extremity subsystem.

Lower extremity control and dynamics during backward angular impulse generation in backward translating tasks.

Observation of complex whole-body movements suggests that the nervous system coordinates multiple operational subsystems using some type of hierarchical control. When comparing two backward translating tasks performed with and without backward angular impulse, we have learned that task-specific modifications in trunk-leg coordination contribute to the regulation of total-body center of mass (CoM) position relative to the reaction force (RF). In this study, we hypothesized that task-specific differences in trunk-leg coordination would affect the control of the lower extremity joints during the impulse-generation phase of the tasks. Eight highly skilled performers executed a series of backward translating jumps with and without backward rotation (back somersault and back timer, respectively). Sagittal plane kinematics, RFs and electromyograms of lower extremity muscles were acquired during the take-off phase of both tasks. Lower extremity joint kinetics was calculated using inverse dynamics. The results indicate that between-task differences in the relative angles between the lower extremity segments and the net joint forces/RF contributed to significant reductions in knee-extensor net joint moments and increases in hip-extensor net joint moments during the push interval of the back somersault as compared to the back timer. Between-task differences in backward trunk angular velocity also contributed to the re-distribution of work done by the lower extremity net joint moments. Between-task differences in lower extremity joint kinetics were associated with synergistic activation of the bi-articular muscles crossing the knee and hip. These results indicated that task-specific control of CoM relative to the RF in order to regulate the backward angular-impulse-involved modification in the control and dynamics of the knee and hip joints. These results indicate that between-task differences in the control objectives at the total-body level (position of CoM relative to the RF) alters the control and dynamics of the multi-joint lower extremity subsystem.

Modifying center of mass trajectory during sit-to-stand tasks redistributes the mechanical demand across the lower extremity joints.

OBJECTIVE: Sit-to-stand tasks are commonly facilitated by modifying the initial position of the center of mass relative to the feet. It was hypothesized that modifications in the center of mass trajectory during sit-to-stand tasks altered the total body momentum at seat departure and redistributed the lower extremity net joint moments. DESIGN: Between-task within-subject comparison was employed using a robust statistical method to accommodate for small sample size. METHODS: Six individuals performed four sit-to-stand tasks with systematic modifications in the initial center of mass position by varying the orientation of the lower extremity segments. The momentum of the center of mass and lower extremity net joint moments were quantified and compared. RESULTS: Reducing the horizontal center of mass displacement significantly reduced horizontal total body momentum required at seat departure. Sit-to-stand tasks initiated with more horizontal shank and thigh positions required significantly greater knee and hip extensor net joint moments than those with more vertical shank and thigh positions. Sit-to-stand tasks initiated with vertical shank positions also required significantly greater hip extensor net joint moments as compared to those with more horizontal shank orientations. INTERPRETATION: When changes in initial center of mass position are made, alteration in center of mass horizontal momentum and the orientation of the lower extremity segments relative to the reaction force are observed. Consequently, mechanical demand imposed on the ankle, knee, and hip joint is redistributed. The magnitude of the net joint moments is dependent on the segment orientation, the reaction force, and the adjacent net joint moment.

Kinetic size selection mechanisms in heteroepitaxial quantum dot molecules.

Heteroepitaxial growth of Si(0.7)Ge(0.3)/Si(001) films under kinetically limited conditions leads to self-assembly of fourfold quantum dot molecules. These structures obtain a narrowly selected maximum size, independent of film thickness or annealing time. Size selection arises from efficient adatom trapping inside the central pit of the quantum dot molecule when the surrounding islands cojoin to form a continuous wall. Self-limiting growth of nanostructures has significant implications for novel nanoelectronic device architectures such as quantum cellular automata.

Mechanical demand and multijoint control during landing depend on orientation of the body segments relative to the reaction force.

The purpose of this study was to determine how diverse momentum conditions and anatomical orientation at contact influences mechanical loading and multijoint control of the reaction force during landings. Male collegiate gymnasts (n=6) performed competition style landings (n=3) of drop jumps, front saltos, and back saltos from a platform (0.72 m) onto landing mats (0.12 m). Kinematics (200 fps), reaction forces (800 Hz) and muscle activation patterns (surface EMG, 1600 Hz) of seven lower extremity muscles were collected simultaneously. Between-task differences in segment orientation relative to the reaction force contributed to significant between-task differences in knee and hip net joint moments (NJM) during the impact phase. During the stabilization phase, ankle, knee, and hip NJMs acted to control joint flexion. Between-task differences in muscle activation patterns indicated that gymnasts scaled biarticular muscle activation to accommodate for between-task differences in NJM after contact. Activation of muscles on both sides of the joint suggests that impedance like control was used to stabilize the joints and satisfy the mechanical demand imposed on the lower extremity. Between-subject differences in the set of muscles used to control total body center of mass (TBCM) trajectory and achieve lower extremity NJMs suggests that control of multijoint movements involving impact needs to incorporate mechanical objectives at both the total body and local level. The functional consequences of such a control structure may prove to be an asset to gymnasts, particularly when required to perform a variety of landing tasks under a variety of environmental constraints.

Subject specific coordination of two- and one-joint muscles during landings suggests multiple control criteria.

The target article, thoughtfully constructed by Dr. Prilutsky, effectively synthesizes available data on multijoint movements regarding coordination patterns of major two- and one-joint muscles, provides evidence for an optimization criterion that predicts critical features of muscle activation patterns, and explores the functional consequences of muscle coordination. This work also provides a clear set of definitions and an organizational framework that is currently needed for a productive interdisciplinary discussion regarding the underlying control mechanisms used during realistic multijoint movements. Although identification of an optimization criterion that predicts muscle recruitment strategies would greatly simplify control logic required for rehabilitation and musculoskeletal modeling, our experimental data during landings indicate more than one criterion may exist. Preliminary review of our experimental landing data suggests the rules identified by Prilutsky apparently hold for some subjects during portions of the landing movements. The presence of more than one muscle activation pattern used to achieve the same NJMs demonstrates there may be more than one optimization criterion that predicts critical features of muscle activation patterns. The functional consequences of more than one control criterion may also prove to be an asset, particularly when adapting to different environmental constraints.

Peer reviewed: understanding microcontaminants in recycled water.

Increasing attention is being given to the detection, treatment, and removal of problematic effluent-derived contaminants.

Periodontal treatment for elderly patients.

The largest growing segment of our society is that of older adults. The population explosion of older adults challenges both general practitioners and periodontists to provide the highest level of care available. More of our patients will have concurrent medical conditions that alter or modify the delivery and provision of periodontal care. This paper reviews some of the common conditions occurring in the older patient and suggests some modifications in periodontal therapy which may be beneficial. The therapist must be knowledgeable about the medications commonly used for treating the chronic diseases of the older population. Finally, the therapist must become adept in performing functional assessments of patients so that the types of therapy administered contribute to the quality of life desired by patients.

Periodontal treatment for elderly patients.

The largest growing segment of our society is that of older Americans. The population explosion of older adults challenges both general practitioners and periodontists to provide the highest level of care available. More of our patients will have concurrent medical conditions that alter or modify the delivery and provision of periodontal care. This paper reviews some of the common conditions occurring in the older patient and suggests some modifications in periodontal therapy which may be beneficial. The therapist must be knowledgeable about the medications commonly used for treating the chronic diseases of the older population. Finally, the therapist must become adept in performing functional assessments of patients so that the types of therapy administered contribute to the quality of life desired by patients.

Acute hemodynamic changes during carotid artery stenting.

To determine the clinical significance of acute hemodynamic disturbances during stenting in the carotid sinus region, we assessed the relation between intraprocedural changes in heart rate (HR) and blood pressure (BP) and adverse neurologic and cardiac outcomes. Eighteen patients underwent carotid stenting with the Wallstent (Schneider Inc). Suitable candidates had at least 60% diameter stenosis of the carotid artery by angiography. Initial and nadir HR and BP were recorded during the predilatation, stent delivery, and postdilatation periods. Bradycardia was defined as HR < or =60 beats/min and hypotension as systolic BP < or =100 mm Hg. Nineteen Wallstents were successfully deployed in all 19 carotid arteries. Some degree of bradycardia or hypotension occurred in 68% of carotid stent procedures, but administration of vasoactive medications was necessary in only 7 patients (37%) with more persistent hemodynamic disturbances. Hypotension or the need for continuous vasopressor therapy was significantly more common during postdilatation (32%) than in the predilatation period (5%) (p = 0.02). Bradycardia was not reduced by prophylactic atropine. In 1 patient the hemodynamic response to stenting may have contributed to an adverse neurologic and cardiac outcome. Thus, despite frequent fluctuations in HR and BP, most carotid stenting procedures were performed with excellent overall results, even in patients at high risk.

Guided tissue regeneration. Nonabsorbable barriers.

Nonabsorbable barriers are considered the material by which all other barriers are judged. They have a well-established record of safety and efficacy. They are not a panacea, however. Practitioners must take special care when selecting both patients and surgical sites for GTR. Extensive experience, superior surgical ability, and meticulous attention to detail are also required if one is to achieve predictably favorable results.

Local effects of nitric oxide supplementation and suppression in the development of intimal hyperplasia in experimental vein grafts.

OBJECTIVES: The universal response of vein grafts after insertion into the arterial circulation is the development of intimal hyperplasia; smooth muscle cell proliferation and connective tissue deposition, which may be modulated in part by dysfunctional endothelial nitric oxide (NO) metabolism. This study examines the effects of single dose, local application by pluronic gel of a NO donor, S-nitroso-N-acetylpenicillamine (SNAP) and an NO synthase inhibitor nitro-L-arginine methyl ester (L-NAME) on the formation of intimal hyperplasia. MATERIALS: Forty New Zealand white rabbits underwent jugular vein interposition grafting of the common carotid artery. DESIGN: Ten animals were controls, 10 animals had the outer surface of the vein graft coated with 30% pluronic gel (2.5 ml), and 10 each were immersed for 15 min prior to insertion in Ringer lactate containing 10(-3) M of SNAP or L-NAME and then had their vein grafts coated with 2.5 ml of gel containing either SNAP (10(-3) M) or L-NAME (10(-3) M), which allows for sustained delivery for up to 6 h. On the 28th post operative day, the animals were sacrificed and vein grafts were harvested for morphology by electron microscopy (SEM and TEM) and dimensional analysis by videomorphometry. RESULTS: All vein grafts developed intimal hyperplasia. On SEM the vein grafts had a confluent layer of endothelial cells with multiple layers of smooth muscle cells representing intimal hyperplasia in TEM. There were no demonstrable morphological differences between the four groups. Local treatment with SNAP produced a significant 36% decrease in mean intimal thickness (72 +/- 4 microns vs. 45 +/- 4 microns; mean +/- S.E.M.; p < 0.01) without a change in medial thickness compared to gel-only treated groups (58 +/- 6 microns vs. 61 +/- 7 microns; p = ns). Inhibition of NO synthase by L-NAME had no effect on the development of intimal hyperplasia (72 +/- 4 microns vs. 79 +/- 10 microns; p = ns); medial thickness was also unchanged. CONCLUSION: These data confirm the protective effect of NO in vascular injury and suggest that NO synthase activity is either absent or reduced to such a level that further inhibition in this short time course is not relevant to the pathophysiology of vein graft intimal hyperplasia.