Phases of cortical actomyosin dynamics coupled to the neuroblast polarity cycle

The Par complex dynamically polarizes to the apical cortex of asymmetrically dividing Drosophila neuroblasts where it directs fate determinant segregation. Previously we showed that apically directed cortical movements that polarize the Par complex require F-actin (Oon and Prehoda, 2019). Here we report the discovery of cortical actomyosin dynamics that begin in interphase when the Par complex is cytoplasmic but ultimately become tightly coupled to cortical Par dynamics. Interphase cortical actomyosin dynamics are unoriented and pulsatile but rapidly become sustained and apically-directed in early mitosis when the Par protein aPKC accumulates on the cortex. Apical actomyosin flows drive the coalescence of aPKC into an apical cap that is depolarized in anaphase when the flow reverses direction. Together with the previously characterized role of anaphase flows in specifying daughter cell size asymmetry, our results indicate that multiple phases of cortical actomyosin dynamics regulate asymmetric cell division.

Coupling between Trigeminal-Induced Asymmetries in Locus Coeruleus Activity and Cognitive Performance

In humans, the asymmetry in the masseter electromyographic (EMG) activity during clenching is positively correlated with the degree of pupil size asymmetry (anisocoria) at rest. Anisocoria reveals an asymmetry in LC activity, which may lead to an imbalance in cortical excitability, detrimental to performance. Hereby, we investigated, in individual subjects, the possibility that occlusal correction, which decreases EMG asymmetry, improves performance by balancing LC activity. Cognitive performance, task-related mydriasis, and pupil size at rest were modified by changing the occlusal condition. Occlusal-related changes in performance and mydriasis were negatively correlated with anisocoria changes in only 12/20 subjects. Within this population, spontaneous fluctuations in mydriasis and anisocoria also appeared negatively coupled. Occlusal-related changes in performance and mydriasis were negatively correlated with those in average pupil size (a proxy of average LC activity) in 19/20 subjects. The strongest association was observed for the pupil changes occurring on the side with higher EMG activity during clenching. These findings indicate that the effects of occlusal conditions on cognitive performance were coupled to changes in the asymmetry of LC activity in about half of the subjects, while they were related to changes in the average tonic LC activity in virtually all of them.

Strategic management in local hospital markets: service duplication or service differentiation

Background The purpose of this study is to assess the influences of market structure on hospitals’ strategic decision to duplicate or differentiate services and to assess the relationship of duplication and differentiation to hospital performance. This study is different from previous research because it examines how a hospital decides which services to be duplicated or differentiated in a dyadic relationship embedded in a complex competitive network. Methods We use Linear Structural Equations (LISREL) to simultaneously estimate the relationships among market structure, duplicated and differentiated services, and performance. All non-federal, general acute hospitals in urban counties in the United States with more than one hospital are included in the sample (n = 1726). Forty-two high-tech services are selected for the study. Data are compiled from the American Hospital Association Annual Survey of Hospitals, Area Resource File, and CMS cost report files. State data from HealthLeaders-InterStudy for 2015 are also used. Results The findings provide support that hospitals duplicate and differentiate services relative to rivals in a local market. Size asymmetry between hospitals is related to both service duplication (negatively) and service differentiation (positively). With greater size asymmetry, a hospital utilizes its valuable resources for its own advantage to thwart competition from rivals by differentiating more high-tech services and reducing service duplication. Geographic distance is positively related to service duplication, with duplication increasing as distance between hospitals increases. Market competition is associated with lower service duplication. Both service differentiation and service duplication are associated with lower market share, higher costs, and lower profits. Conclusions The findings underscore the role of market structure as a check and balance on the provision of high-tech services. Hospital management should consider cutting back some services that are oversupplied and/or unprofitable and analyze the supply and demand in the market to avoid overdoing both service duplication and service differentiation.

Peripheral microtubules ensure asymmetric furrow positioning in neural stem cells

Neuroblast (NB) cell division is characterized by a basal positioning of the cleavage furrow resulting in a large difference in size between the future daughter cells. In animal cells, furrow placement and assembly is governed by centralspindlin, a highly conserved complex that accumulates at the equatorial cell cortex of the future cleavage site and at the spindle midzone. In contrast to model systems studied so far, these two centralspindlin populations are spatially and temporally separated in NBs. A cortical leading pool is located at the basal cleavage furrow site and a second pool accumulates at the midzone before travelling to the site of the basal cleavage furrow during cytokinesis completion. By manipulating microtubule (MT) dynamics, we show that the cortical centralspindlin population requires peripheral astral microtubules and the Chromosome Passenger Complex (CPC) for efficient recruitment. Loss of this pool does not prevent cytokinesis but enhances centralspindlin levels at the midzone leading to furrow repositioning towards the equator and decreased size asymmetry between daughter cells. Together these data reveal that the asymmetrical furrow placement characteristic of NBs results from a competition between spatially and functionally separate centralspindlin pools in which the cortical pool is dominant and requires peripheral astral microtubules.

Strategic Management in Local Hospital Markets: Service Duplication or Service Differentiation

Background: The purpose of this study is to assess the influences of market structure on hospitals’ strategic decision to duplicate or differentiate services and to assess the relationship of duplication and differentiation to hospital performance. This study is different from previous research because it examines how a hospital decides which services to be duplicated or differentiated in a dyadic relationship embedded in a complex competitive network. Methods: We use Linear Structural Equations (LISREL) to simultaneously estimate the relationships among market structure, duplicated and differentiated services, and performance. All non-federal, general acute hospitals in urban counties in the United States with more than one hospital are included in the sample (n=1726). Forty-two high-tech services are selected for the study. Data are compiled from the American Hospital Association Annual Survey of Hospitals, Area Resource File, and CMS cost report files. State data from HealthLeaders-InterStudy for 2015 are also used.Results: The findings provide support that hospitals duplicate and differentiate services relative to rivals in a local market. Size asymmetry between hospitals is related to both service duplication (negatively) and service differentiation (positively). With greater size asymmetry, a hospital utilizes its valuable resources for its own advantage to thwart competition from rivals by differentiating more high-tech services and reducing service duplication. Geographic distance is positively related to service duplication, with duplication increasing as distance between hospitals increases. Market competition is associated with lower service duplication. Both service differentiation and service duplication are associated with lower market share, higher costs, and lower profits. Conclusions: The findings underscore the role of market structure as a check and balance on the provision of high-tech services. Hospital management should consider cutting back some services that are oversupplied and/or unprofitable and analyze the supply and demand in the market to avoid overdoing both service duplication and service differentiation.

A Case of Mistaken Identity of a Mesiodens

This case report discusses the characteristics, sequelae and management of the supernumerary tooth in a developing dentition, particularly the mesiodens. The case describes when an eruption of a mesiodens was misdiagnosed as a microdont maxillary central incisor, leading to ectopic and late eruption of the permanent maxillary incisor. This case highlights the importance of clinical and radiographic investigation where tooth size asymmetry is observed in the upper anterior region. CPD/Clinical Relevance: The incidence of a single microdont maxillary central incisor is rare and is not known to be documented in the literature. If a small tooth erupts in the midline it should be considered a supernumerary tooth until proven otherwise. Further clinical and radiographic investigation should be performed to determine the presence and location of the maxillary central incisor(s).

Structural Properties of the Fluid Mixture Confined by a Semipermeable Membrane: A Density Functional Study

Classical density functional theory (DFT) is employed to study the structural properties of a binary fluid mixture confined by a semipermeable membrane. The influences of volume fraction and size asymmetry on three characteristic densities and excess adsorption are investigated in detail. In addition, some of our results are calculated by the analytical method, which agree well with those from the DFT calculations. These results may provide helpful clues to understand the structural properties of other complex fluids or mixture confined by semipermeable membrane.