Phanostrate and the Legitimization of Professional Female Healers in Fourth Century Athens

The goal of this paper is to discuss the origins of female medical professionals and to explore the ways in which ancient female healers represented themselves. I argue that in fourth century Athens, legitimacy as a female medical professional in the eyes of doctors and the whole polis comes from a combination of using masculinized language to engage in medical discourse and feminine self-representation to expand the ideal of a “respectable woman.” Phanostrate’s funerary monument is the first look into how female healers legitimized themselves in the professional medical world, and so using her as a model, we can better understand the evolving world of professionalized medicine

Does having a Master of Public Health (MPH) improve physician assistants’ ability to address the social determinants of health in their clinical practice?

Background: There is mounting evidence that clinicians need to address the social determinants of heath (SDOH) in their practice. Physician Assistants (PAs) who complete a joint degree with a Master of Public Health (MPH) may be able to address the SDOH in their practice better than those who do not have the degree. The primary aim of this study was to determine whether or not having a Master in Public Health (MPH) improves PAs’ ability to address the SDOH in their clinical practice. Methods: A cross-sectional study was conducted with 25 practicing PAs who were jointly trained with the MPH degree and 32 practicing PAs who were not jointly trained. An online survey was administered to a gather SDOH knowledge, attitude and behavior data using an adapted 13-item SDOH scale. Results: This study found that jointly trained PA/MPH clinicians reported significantly more perceived knowledge about SDOH (37.6 vs 31.1; P = .028), were more likely to identify SDOHs as important to their patients’ health (38.6 vs 32.9; P = .035), were more likely to intend to address SDOH with their patients’ (29.7 vs 23.5; P = .031) and reported feeling more comfortable talking about SDOH with their patients (3.75 vs 3.2; P = .05) despite no significant differences in reported barriers to addressing SDOH. Conclusion: These findings suggest that joint clinical training with the MPH can positively impact PAs ability to address the SDOH in their clinical work and lays the groundwork for future research

ATPase mechanism of the 5'-3' DNA helicase, RecD2: evidence for a pre-hydrolysis conformation change

The superfamily 1 helicase, RecD2, is a monomeric, bacterial enzyme with a role in DNA repair, but with 5'-3' activity unlike most enzymes from this superfamily. Rate constants were determined for steps within the ATPase cycle of RecD2 in the presence of ssDNA. The fluorescent ATP analog, mantATP (2'(3')-O-(N-methylanthraniloyl)ATP), was used throughout to provide a complete set of rate constants and determine the mechanism of the cycle for a single nucleotide species. Fluorescence stopped-flow measurements were used to determine rate constants for adenosine nucleotide binding and release, quenched-flow measurements were used for the hydrolytic cleavage step, and the fluorescent phosphate biosensor was used for phosphate release kinetics. Some rate constants could also be measured using the natural substrate, ATP, and these suggested a similar mechanism to that obtained with mantATP. The data show that a rearrangement linked to Mg(2+) coordination, which occurs before the hydrolysis step, is rate-limiting in the cycle and that this step is greatly accelerated by bound DNA. This is also shown here for the PcrA 3'-5' helicase and so may be a general mechanism governing superfamily 1 helicases. The mechanism accounts for the tight coupling between translocation and ATPase activity

Hypothesis: bacterial clamp loader ATPase activation through DNA-dependent repositioning of the catalytic base and of a trans-acting catalytic threonine

The prokaryotic DNA polymerase III clamp loader complex loads the β clamp onto DNA to link the replication complex to DNA during processive synthesis and unloads it again once synthesis is complete. This minimal complex consists of one δ, one δ′ and three γ subunits, all of which possess an AAA+ module—though only the γ subunit exhibits ATPase activity. Here clues to underlying clamp loader mechanisms are obtained through Bayesian inference of various categories of selective constraints imposed on the γ and δ′ subunits. It is proposed that a conserved histidine is ionized via electron transfer involving structurally adjacent residues within the sensor 1 region of γ's AAA+ module. The resultant positive charge on this histidine inhibits ATPase activity by drawing the negatively charged catalytic base away from the active site. It is also proposed that this arrangement is disrupted upon interaction of DNA with basic residues in γ implicated previously in DNA binding, regarding which a lysine that is near the sensor 1 region and that is highly conserved both in bacterial and in eukaryotic clamp loader ATPases appears to play a critical role. γ ATPases also appear to utilize a trans-acting threonine that is donated by helix 6 of an adjacent γ or δ′ subunit and that assists in the activation of a water molecule for nucleophilic attack on the γ phosphorous atom of ATP. As eukaryotic and archaeal clamp loaders lack most of these key residues, it appears that eubacteria utilize a fundamentally different mechanism for clamp loader activation than do these other organisms

Structures of smooth muscle myosin and heavy meromyosin in the folded, shutdown state

Remodelling of the contractile apparatus within smooth muscle cells is an essential process that allows effective contractile activity over a wide range of cell lengths. The thick filaments may be redistributed via depolymerisation into inactive myosin monomers that have been detected in vitro, in which the long tail has a folded conformation. The structure of this folded molecule has been controversial. Using negative stain electron microscopy of individual folded molecules from turkey gizzard we show they are more compact than previously described, with heads and the three segments of the folded tail closely packed. Smooth muscle heavy meromyosin (HMM), which lacks two-thirds of the tail, closely resembles the equivalent parts of whole myosin. Image processing reveals a characteristic head region morphology for both HMM and myosin whose features are identifiable by comparison with less compact molecules. The two heads associate asymmetrically: the tip of one motor domain touches the base of the other, resembling the blocked and free heads of this HMM when it forms 2-D crystals on lipid. The tail of HMM lies between the heads, contacting the blocked motor domain, unlike in the 2-D crystal. The tail of the intact myosin is bent sharply and consistently at two positions close to residues 1175 and 1535. The first bend position correlates with a skip in the coiled coil sequence, the second does not. The first segment runs between the heads from the head-tail junction. Unexpectedly, the other segments associate only with the blocked head rather than both heads, such that the second bend lies at a specific position near the C-lobe of the blocked head regulatory light chain. Quantitative analysis of tail flexibility shows that the single coiled coil of HMM has an apparent Young’s modulus of about 0.5 GPa. The folded tail of the intact molecule is less flexible indicating interactions between the segments. The folded tail does not modify the compact head arrangement but stabilises it, indicating a structural mechanism for the very low ATPase activity of the folded molecule

Substrate and Product Dependence of Force and Shortening in Fast and Slow Smooth Muscle

To explore the molecular mechanisms responsible for the variation in smooth muscle contractile kinetics, the influence of MgATP, MgADP, and inorganic phosphate (Pi) on force and shortening velocity in thiophosphorylated “fast” (taenia coli: maximal shortening velocity Vmax = 0.11 ML/s) and “slow” (aorta: Vmax = 0.015 ML/s) smooth muscle from the guinea pig were compared. Pi inhibited active force with minor effects on the Vmax. In the taenia coli, 20 mM Pi inhibited force by 25%. In the aorta, the effect was markedly less (<10%), suggesting differences between fast and slow smooth muscles in the binding of Pi or in the relative population of Pi binding states during cycling. Lowering of MgATP reduced force and Vmax. The aorta was less sensitive to reduction in MgATP (Km for Vmax: 80 μM) than the taenia coli (Km for Vmax: 350 μM). Thus, velocity is controlled by steps preceding the ATP binding and cross-bridge dissociation, and a weaker binding of ATP is not responsible for the lower Vmax in the slow muscle. MgADP inhibited force and Vmax. Saturating concentrations of ADP did not completely inhibit maximal shortening velocity. The effect of ADP on Vmax was observed at lower concentrations in the aorta compared with the taenia coli, suggesting that the ADP binding to phosphorylated and cycling cross-bridges is stronger in slow compared with fast smooth muscle

Functional characterization of the human myosin-7a motor domain

Myosin-7a participates in auditory and visual processes. Defects in MYO7A, the gene encoding the myosin-7a heavy chain, are causative for Usher syndrome 1B, the most frequent cause of deaf-blindness in humans. In the present study, we performed a detailed kinetic and functional characterization of the isolated human myosin-7a motor domain to elucidate the details of chemomechanical coupling and the regulation of motor function. A rate-limiting, slow ADP release step causes long lifetimes of strong actin-binding intermediates and results in a high duty ratio. Moreover, our results reveal a Mg2+-sensitive regulatory mechanism tuning the kinetic and mechanical properties of the myosin-7a motor domain. We obtained direct evidence that changes in the concentration of free Mg2+ ions affect the motor properties of human myosin-7a using an in vitro motility assay system. Our results suggest that in a cellular environment, compartment-specific fluctuations in free Mg2+ ions can mediate the conditional switching of myosin-7a between cargo moving and tension bearing modes