A metabolite-sensitive, thermodynamically-constrained model of\ud cardiac cross-bridge cycling: Implications for force development during ischemia

We present a metabolically regulated model of cardiac active force generation with which we investigate the effects of ischemia on maximum forceproduction. Our model, based on the Rice et al. (2008) model of cross-bridge kinetics, reproduces many of the observed effects of MgATP, MgADP, Pi and H+ on force development while still retaining the force/length/Ca2+ properties of the original model. We introduce three new parameters to account for the competitive binding of H+ to the Ca2+ binding site on troponin C and the binding of MgADP within the cross-bridge cycle. These parameters along with the Pi and H+ regulatory steps within the cross-bridge cycle were constrained using data from the literature and validated using a range of metabolic and sinusoidal length perturbation protocols. The placement of the MgADP binding step between two strongly-bound and force-generating states leads to the emergence of an unexpected effect on the force-MgADP curve, where the trend of the relationship (positive or negative) depends on the concentrations of the other metabolites and [H+]. The model is used to investigate the sensitivity of maximum force production to changes in metabolite concentrations during the development of ischemia

Deletion of EP4 in S100a4-lineage cells reduces scar tissue formation during early but not later stages of tendon healing

AbstractTendon injuries heal via scar tissue rather than regeneration. This healing response forms adhesions between the flexor tendons in the hand and surrounding tissues, resulting in impaired range of motion and hand function. Mechanistically, inflammation has been strongly linked to adhesion formation, and Prostaglandin E2 (PGE2) is associated with both adhesion formation and tendinopathy. In the present study we tested the hypothesis that deletion of the PGE2 receptor EP4 in S100a4-lineage cells would decrease adhesion formation. S100a4-Cre; EP4flox/flox (EP4cKOS100a4) repairs healed with improved gliding function at day 14, followed by impaired gliding at day 28, relative to wild type. Interestingly, EP4cKOS100a4 resulted in only transient deletion of EP4, suggesting up-regulation of EP4 in an alternative cell population in these mice. Loss of EP4 in Scleraxis-lineage cells did not alter gliding function, suggesting that Scx-lineage cells are not the predominant EP4 expressing population. In contrast, a dramatic increase in α-SMA+, EP4+ double-positive cells were observed in EP4cKOS100a4 suggesting that EP4cKOS100a4 repairs heal with increased infiltration of EP4 expressing α-SMA myofibroblasts, identifying a potential mechanism of late up-regulation of EP4 and impaired gliding function in EP4cKOS100a4 tendon repairs.</jats:p

COVID-19 lockdown improved river water quality in China

The impacts of COVID-19 lockdowns on air quality around the world have received wide attention. In comparison, assessments of the implications for water quality are relatively rare. As the first country impacted by COVID-19, China implemented local and national lockdowns that shut down industries and businesses between January and May 2020. Based on monthly field measurements (N = 1693) and daily automonitoring (N = 65), this study analyzed the influence of the COVID-19 lockdown on river water quality in China. The results showed significant improvements in river water quality during the lockdown period but out-of-step improvements for different indicators. Reductions in ammonia nitrogen (NH4+-N) began relatively soon after the lockdown; chemical oxygen demand (COD) and dissolved oxygen (DO) showed improvements beginning in late January/early February and mid-March, respectively, while increases in pH were more temporally concentrated in the period from mid-March to early May. Compared to April 2019, the Water Quality Index increased at 67.4% of the stations in April 2020, with 75.9% of increases being significant. Changes in water quality parameters also varied spatially for different sites and were mainly determined by the locations and levels of economic development. After the lifting of the lockdown in June, all water quality parameters returned to pre-COVID-19 lockdown conditions. Our results clearly demonstrate the impacts of human activities on water quality and the potential for reversing ecosystem degradation by better management of wastewater discharges to replicate the beneficial impacts of the COVID-19 lockdown. Capsule summary: River water quality improved during China's COVID-19 lockdown, but returned to normal conditions after the lockdown

Research Notes: Soybean Gene Resources Recently Received from China

Forty soybean cultivars were received from the Peoples Republic of China in a number of exchanges between June 1973 and June 1974. The first eight cultivars that we received were grown in row tests at Harrow, Woodslee and Ridgetown in 1975, along with \u27Harlen,\u27 \u27Harosoy 63,\u27 and \u27Harcar.\u27 These eight, plus the next seven that we received, had been tested in hill plots at Harrow in 1974, along with Hardome, Harlen, Harosoy 63, and \u27Harwood.\u27 The highest and lowest cultivar values are given for each of a number of characteristics within each group of cultivars as an indication of the potential value of the new germplasm

Parent-Adolescent Socialization of Social Class in Low Income White Families: Theory, Research, & Future Directions

The formative role of social class in the United States has long been a focus of fields such as economics, history, and political science. Yet, little psychological theory or data are available to guide our understanding of what messages regarding social class are transmitted within and across generations and how those transmissions are most likely to occur. As a launching point for such work, we focus this initial contextual and largely theoretical review on parent–adolescent socialization of social class in low‐income, White families of adolescents in particular. To this end, our goal was to raise potential hypotheses about the implicit and explicit ways that White low‐income parents may shape adolescent views of class, as well as the meaning and implications of status socialization for adolescent health and well‐being

Resolving an inconsistency in the estimation of the energy for excitation of cardiac muscle contraction

In the excitation of muscle contraction, calcium ions interact with transmembrane transporters. This process is accompanied by energy consumption and heat liberation. To quantify this activation energy or heat in the heart or cardiac muscle, two non-pharmacological approaches can be used. In one approach using the “pressure-volume area” concept, the same estimate of activation energy is obtained regardless of the mode of contraction (either isovolumic/isometric or ejecting/shortening). In the other approach, an accurate estimate of activation energy is obtained only when the muscle contracts isometrically. If the contraction involves muscle shortening, then an additional component of heat associated with shortening is liberated, over and above that of activation. The present study thus examines the reconcilability of the two approaches by performing experiments on isolated muscles measuring contractile force and heat output. A framework was devised from the experimental data to allow us to replicate several mechanoenergetics results gleaned from the literature. From these replications, we conclude that the choice of initial muscle length (or ventricular volume) underlies the divergence of the two approaches in the estimation of activation energy when the mode of contraction involves shortening (ejection). At low initial muscle lengths, the heat of shortening is relatively small, which can lead to the misconception that activation energy is contraction mode independent. In fact, because cardiac muscle liberates heat of shortening when allowed to shorten, estimation of activation heat must be performed only under isometric (isovolumic) contractions. We thus recommend caution when estimating activation energy using the “pressure-volume area” concept

Technology-Enhanced Behavioral Parent Training: The Relationship Between Technology Use and Efficiency of Service Delivery

Behavior disorders (BDs) are common and, without treatment, can have long-term impacts on child and family health. Behavioral Parent Training (BPT) is the standard of care intervention for early-onset BDs; however, structural socioeconomic barriers hinder treatment outcomes for low-income families. While digital technologies have been proposed as a mechanism to improve engagement in BPT, research exploring the relationship between technology use and outcomes is lacking. Thus, this study with 34 low-income families examined the impact of parents' use of adjunctive mobile app components on treatment efficiency in one technology-enhanced (TE-) BPT program, Helping the Noncompliant Child (HNC). While parent use of the TE-HNC app and its impact on the efficiency of service delivery varied across specific components, increased app use significantly reduced the number of weeks required for families to achieve skill mastery. Implications for the design and development of behavior intervention technologies in general, as well as for BPT in particular, are discussed

Observations of water transparency in China's lakes from space

Water transparency, usually denoted by Secchi disk depth (SSD), represents the first-order description of water quality and has important implications for the diversity and productivity of aquatic life. In China, lakes supply freshwater and ecosystem services to nearly a billion people. Therefore, real time monitoring of lake transparency is of great significance. Moreover, understanding how and why transparency varies in space and time in response to different driving forces is needed to understand, manage, and predict lake water quality. Based on the time-saving and low-cost Google Earth Engine cloud platform, this study developed a new algorithm for quickly mapping SDDs in Chinese lakes. SDDs were retrieved for 412 Chinese lakes (> 20 km2) for the period 2000–2018. Results demonstrated that lake water depth spatially differentiated transparency. Deep lakes usually had high transparency and water depth explained 88.81 % of the spatial variations. With increasing catchment vegetation coverage and lake water depth, 70.15 % of lakes witnessed increasing transparency during 2000–2018. Of these 42.72 % were significant (p<0.05). Transparency of deep lakes was generally determined by phytoplankton density not sediment resuspension. Minimum transparency occurred in summer. Future increases in lake water levels in response to factors such as climate change may contribute to further improvements in transparency. Management should focus on controlling eutrophication and increasing vegetation cover in catchments