Morphological Studies of Solution-Crystallized Thermoplastic Elastomers with Polyethylene Endblocks and a Random-Copolymer Midblock.

Styrenic thermoplastic elastomers (TPEs) in the form of triblock copolymers possessing glassy endblocks and a rubbery midblock account for the largest global market of TPEs worldwide, and typically rely on microphase separation of the endblocks and the subsequent formation of rigid microdomains to ensure satisfactory network stabilization. In this study, the morphological characteristics of a relatively new family of crystallizable TPEs that instead consist of polyethylene endblocks and a random-copolymer midblock composed of styrene and (ethylene-co-butylene) moieties are investigated. Copolymer solutions prepared at logarithmic concentrations in a slightly endblock-selective solvent are subjected to crystallization under different time and temperature conditions to ascertain if copolymer self-assembly is directed by endblock crystallization or vice versa. According to transmission electron microscopy, semicrystalline aggregates develop at the lowest solution concentration examined (0.01 wt%), and the size and population of crystals, which dominate the copolymer morphologies, are observed to increase with increasing aging time. Real-space results are correlated with small- and wide-angle X-ray scattering to elucidate the concurrent roles of endblock crystallization and self-assembly of these unique TPEs in solution.

Network topology and stability of homologous multiblock copolymer physical gels.

The mechanical properties of physical gels generated by selectively swelling a homologous series of linear multiblock copolymers are investigated by quasistatic uniaxial tensile tests. We use the slip-tube network model to extract the contributions arising from network crosslinks and chain entanglements. The composition dependence of these contributions is established and considered in terms of simulations that identify the probabilities associated with chain conformations. Dynamic rheology provides additional insight into the characteristics and thermal stability of the molecular networks.

Communication: Molecular-level description of constrained chain topologies in multiblock copolymer gel networks.

Network characteristics in physical gels composed of solvated block copolymers varying in molecular design are examined here by dynamic rheology and computer simulations. In two triblock copolymer series, one with chain length (N) varied at constant copolymer composition (f) and the other with f varied at constant N, we discern the dependence of equilibrium network metrics on both N and f. Increasing the block number in a linear multiblock series at constant N and f escalates conformational complexity, which dominates network connectivity classified according to a midblock conformation index.

Bicomponent Block Copolymers Derived from One or More Random Copolymers as an Alternative Route to Controllable Phase Behavior.

Block copolymers have been extensively studied due to their ability to spontaneously self-organize into a wide variety of morphologies that are valuable in energy-, medical-, and conservation-related (nano)technologies. While the phase behavior of bicomponent diblock and triblock copolymers is conventionally governed by temperature and individual block masses, it is demonstrated here that their phase behavior can alternatively be controlled through the use of blocks with random monomer sequencing. Block random copolymers (BRCs), i.e., diblock copolymers wherein one or both blocks are a random copolymer comprised of A and B repeat units, have been synthesized, and their phase behavior, expressed in terms of the order-disorder transition (ODT), has been investigated. The results establish that, depending on the block composition contrast and molecular weight, BRCs can microphase-separate. We also report that large variation in incompatibility can be generated at relatively constant molecular weight and temperature with these new soft materials. This sequence-controlled synthetic strategy is extended to thermoplastic elastomeric triblock copolymers differing in chemistry and possessing a random-copolymer midblock.

Site-directed mutagenesis of HgcA and HgcB reveals amino acid residues important for mercury methylation.

Methylmercury is a potent neurotoxin that is produced by anaerobic microorganisms from inorganic mercury by a recently discovered pathway. A two-gene cluster, consisting of hgcA and hgcB, encodes two of the proteins essential for this activity. hgcA encodes a corrinoid protein with a strictly conserved cysteine proposed to be the ligand for cobalt in the corrinoid cofactor, whereas hgcB encodes a ferredoxin-like protein thought to be an electron donor to HgcA. Deletion of either gene eliminates mercury methylation by the methylator Desulfovibrio desulfuricans ND132. Here, site-directed mutants of HgcA and HgcB were constructed to determine amino acid residues essential for mercury methylation. Mutations of the strictly conserved residue Cys93 in HgcA, the proposed ligand for the corrinoid cobalt, to Ala or Thr completely abolished the methylation capacity, but a His substitution produced measurable methylmercury. Mutations of conserved amino acids near Cys93 had various impacts on the methylation capacity but showed that the structure of the putative "cap helix" region harboring Cys93 is crucial for methylation function. In the ferredoxin-like protein HgcB, only one of two conserved cysteines found at the C terminus was necessary for methylation, but either cysteine sufficed. An additional, strictly conserved cysteine, Cys73, was also determined to be essential for methylation. This study supports the previously predicted importance of Cys93 in HgcA for methylation of mercury and reveals additional residues in HgcA and HgcB that facilitate the production of this neurotoxin.

Acute calciphylaxis precipitated by the initiation of hemodialysis.

Calciphylaxis, or calcific uremic arteriopathy (CUA), is characterized by metastatic calcification in the media of small arteries and arterioles leading to cutaneous necrosis. It is most commonly seen in patients with end stage renal disease who have elevated serum calcium × phosphorus (Ca × P) product. Normalization of Ca × P product is considered paramount in the prevention and treatment of CUA. We describe a novel presentation of CUA in which a Stage-5 CKD patient developed signs and symptoms of CUA immediately after initiation of hemodialysis (HD). We postulate that an influx of calcium from the dialysate into the patient's blood, in addition to correction of her acidosis, led to abundant substrate in a favorable milieu for Ca-P complex formation at the time of her first HD session. Our case is the first reported case of HD associated iatrogenic acute CUA. To avoid this complication, we should maintain adequate hydration,use lower calcium dialysate, and avoid vitamin D analogues and calcium-containing medications when initiating HD in patients with high Ca-P product. Since sodium thiosulfate is known to prevent precipitation of Ca-P complexes, its empiric use during initial HD treatments may be effective in preventing CUA, a potentially fatal disease.

Rapid and Repetitive Inactivation of SARS-CoV-2 and Human Coronavirus on Self-Disinfecting Anionic Polymers.

While the ongoing COVID-19 pandemic affirms an urgent global need for effective vaccines as second and third infection waves are spreading worldwide and generating new mutant virus strains, it has also revealed the importance of mitigating the transmission of SARS-CoV-2 through the introduction of restrictive social practices. Here, it is demonstrated that an architecturally- and chemically-diverse family of nanostructured anionic polymers yield a rapid and continuous disinfecting alternative to inactivate coronaviruses and prevent their transmission from contact with contaminated surfaces. Operating on a dramatic pH-drop mechanism along the polymer/pathogen interface, polymers of this archetype inactivate the SARS-CoV-2 virus, as well as a human coronavirus surrogate (HCoV-229E), to the minimum detection limit within minutes. Application of these anionic polymers to frequently touched surfaces in medical, educational, and public-transportation facilities, or personal protection equipment, can provide rapid and repetitive protection without detrimental health or environmental complications.

Epidermal growth factor abrogates hypoxia-induced apoptosis in cultured human trophoblasts through phosphorylation of BAD Serine 112.

We tested the hypothesis that epidermal growth factor (EGF) limits hypoxia-induced apoptosis in cultured human trophoblasts by phosphorylation of the proapoptotic protein Bcl-2-associated death promoter (BAD). Cytotrophoblasts were isolated from placentas of uncomplicated pregnancies at 38-40 wk gestation. Primary trophoblasts or transfected JEG3 trophoblast cells were cultured in less than 1 or 20% oxygen in the presence or absence of EGF and signaling pathway inhibitors. BAD, green fluorescent protein (GFP)-BAD, 14-3-3, Bcl-X(L), and neoepitopes formed during apoptotic cleavage of cytokeratin 18 intermediate filaments were quantified using immunoblotting. Cultures immunostained by fluorescent antibodies were analyzed by confocal microscopy for BAD and GFP. Fluorescence resonance energy transfer was used to detect molecular interaction between endogenous BAD and GFP-BAD. We found EGF increased the phosphorylation of BADser112 under standard culture conditions. Whereas hypoxia enhanced apoptosis and increased phosphorylation of both BADser136 and BADser155, hypoxia diminished phosphorylation of BADser112, and this effect was reversible by EGF. Transfected GFP-BAD, which directly interacted with endogenous BAD by colocalization and fluorescence resonance energy transfer, enhanced hypoxia-induced apoptosis in JEG3 cells. EGF reduced apoptosis in hypoxic JEG3 cells that overexpressed GFP-BAD but not in cells overexpressing GFP-BAD that harbored a serine-to-alanine mutation at the 112 site. Coimmunoprecipitation studies showed that EGF reduced the proapoptotic interaction of BAD with Bcl-X(L). The effect of EGF on phosphorylation of BADser112 was dependent on the action of p38 MAPK. We conclude that EGF signals via p38 MAPK to increase phosphorylation of BADser112 and thereby limit trophoblast apoptosis.

Nanoparticle-regulated phase behavior of ordered block copolymers.

Although block copolymer motifs have received considerable attention as supramolecular templates for inorganic nanoparticles, experimental observations of a nanostructured diblock copolymer containing inorganic nanoparticles-supported by theoretical trends predicted from a hybrid self-consistent field/density functional theory-confirm that nanoparticle size and selectivity can likewise stabilize the copolymer nanostructure by increasing its order-disorder transition temperature.

De-moralized: Glucksberg in the malaise.

Ten years down the road, what is the enduring significance of the "assisted suicide" cases, Washington v. Glucksberg and Vacco v. Quill? The cases reflect an unusually earnest, but nonetheless unsuccessful, attempt by the Supreme Court to grapple with a profound moral issue. So, why was the Court unable to provide a more satisfying justification for its conclusions? This Article, written for a symposium on the tenth anniversary of Glucksberg, discusses that question. Part I examines some of the flaws in reasoning in the Glucksberg and Quill opinions and suggests that these flaws stem from the opinion writers' inability to recognize and articulate their underlying normative assumptions. More specifically, both the Justices and the lower court judges, on both sides of the issue, evidently attributed normative significance to something like a "natural course of life" (even when they denied doing so), but none were willing or able to make this attribution explicit. Part II discusses the modern separation of moral reasoning from the metaphysical or theological perspectives that might once have endowed "nature" with normative significance, and it suggests that the deficiencies in Glucksberg-Quill are evidence of how that separation renders moral reasoning problematic. The Conclusion wonders whether in this situation, a renewed emphasis on formalism or tradition might make legal reasoning less unacceptable.

Effect of Systematic Hydrogenation on the Phase Behavior and Nanostructural Dimensions of Block Copolymers.

Unsaturated polydienes are frequently hydrogenated to yield polyolefins that are more chemically stable. Here, the effects of partial hydrogenation on the phase behavior and nanostructure of polyisoprene-containing block copolymers are investigated. To ensure access to the order-disorder transition temperature (TODT) over a wide temperature range, we examine copolymers with at least one random block. Dynamic rheological and scattering measurements indicate that TODT increases linearly with increasing hydrogenation. Small-angle scattering reveals that the temperature-dependence of the Flory-Huggins parameter changes and the microdomain period increases, while the interfacial thickness decreases. The influence of hydrogenation becomes less pronounced in more constrained multiblock copolymers.

Granulomatous Interstitial Nephritis Presenting as Hypercalcemia and Nephrolithiasis.

We report a case of acute kidney injury as the initial manifestation of sarcoidosis. A 55-year-old male was sent from his primary care physician's office with incidental lab findings significant for hypercalcemia and acute kidney injury with past medical history significant for nephrolithiasis. Initial treatment with intravenous hydration did not improve his condition. The renal biopsy subsequently revealed granulomatous interstitial nephritis (GIN). Treatment with the appropriate dose of glucocorticoids improved both the hypercalcemia and renal function. Our case demonstrates that renal limited GIN due to sarcoidosis, although a rare entity, can cause severe acute kidney injury and progressive renal failure unless promptly diagnosed and treated.

Insulin and fatty acids regulate the expression of the fat droplet-associated protein adipophilin in primary human trophoblasts.

OBJECTIVE: This study was undertaken to test the hypothesis that insulin and fatty acids regulate adipophilin expression in cultured human trophoblasts. STUDY DESIGN: Cytotrophoblasts isolated from term human placentas were cultured in the absence or presence of insulin (10 nmol/L), and a mix of oleic and linoleic acid in serum-free medium. The expression of adipophilin as well as the fatty acid transport proteins (FATP) 2, 3, 4 and 6 was examined. Fat accumulation was quantified by BODIPY staining and fat uptake determined using [3H]-oleic acid. RESULTS: A combination of insulin and fatty acids enhanced the expression of adipophilin (2.3-fold, P < .05). In contrast, the expression of FATPs was unchanged. Furthermore, insulin and fatty acids increased the accumulation of fat droplets in trophoblasts by 4- to 5-fold (P < .05), but had no effect on oleic acid uptake. CONCLUSION: Insulin and fatty acids enhance the expression of adipophilin and the formation of fatty acid droplets in term human trophoblasts.

Myocytes of chorionic vessels from placentas with meconium-associated vascular necrosis exhibit apoptotic markers.

Meconium-associated vascular necrosis (MAVN) is a histological abnormality of human placental chorionic vessels that is associated with poor neonatal outcome. We tested the hypothesis that MAVN shows apoptosis in the walls of chorionic vessels. Archival placental specimens with MAVN (n = 5) were compared with specimens from uncomplicated pregnancies at term (n = 5) and from placentas with intense chorionic vasculitis associated with acute chorioamnionitis with (n = 5) or without (n = 5) a clinical history of meconium in the amniotic fluid. Sections from all placentas were processed by the TUNEL method, and 2 observers who were blinded to specimen diagnosis quantified the immunofluorescent TUNEL staining in both the amnion-facing and villous-facing walls of the larger chorionic vessels in each specimen. Compared with the other 3 groups, only the amnion-facing wall of chorionic vessels in MAVN showed a significantly greater number of apoptotic cells. This was verified by morphological criteria and caspase 3 staining. There were limited or no detectable TUNEL-stained cells in either the villous-facing walls of vessels in the MAVN specimens or in any of the vessels of the placentas from uncomplicated pregnancies. There was a negligible level of apoptosis in chorionic vessels of placentas with intense chorionic vasculitis, with or without meconium, despite the inflammatory response or presence of meconium. We conclude that apoptosis contributes to the pathophysiology of MAVN.

Newborn hearing screening with combined otoacoustic emissions and auditory brainstem responses.

Accurate assessment of neonatal hearing screening performance is impossible without knowledge of the true status of hearing, a prohibitive requirement that necessitates a complete diagnostic evaluation on all babies screened. The purpose of this study was to circumvent this limitation by integrating two types of screening measures obtained near simultaneously on every baby. Peripheral auditory function was defined by otoacoustic emission results. A complete diagnostic evaluation was performed on every baby who received a "Refer" outcome for auditory brainstem response screening. The integrated results for auditory brainstem response screening in an unselected group of 300 newborns estimated sensitivity at 100%, specificity at 99.7%, overall referral rate at 2.0%, and a positive predictive value of 83.3%. Conductive loss associated with amniotic fluid in the middle ear can persist several weeks after birth; conductive loss can produce a "Refer" outcome for auditory brainstem response screening; and auditory neuropathy can be detected with screening measures. Prevalence results were consistent with the published literature. The implications of this study are that otoacoustic emissions and auditory brainstem measures provide much more information than either alone and that both are needed for a comprehensive hearing screening program.

The genetic basis for bacterial mercury methylation.

Methylmercury is a potent neurotoxin produced in natural environments from inorganic mercury by anaerobic bacteria. However, until now the genes and proteins involved have remained unidentified. Here, we report a two-gene cluster, hgcA and hgcB, required for mercury methylation by Desulfovibrio desulfuricans ND132 and Geobacter sulfurreducens PCA. In either bacterium, deletion of hgcA, hgcB, or both genes abolishes mercury methylation. The genes encode a putative corrinoid protein, HgcA, and a 2[4Fe-4S] ferredoxin, HgcB, consistent with roles as a methyl carrier and an electron donor required for corrinoid cofactor reduction, respectively. Among bacteria and archaea with sequenced genomes, gene orthologs are present in confirmed methylators but absent in nonmethylators, suggesting a common mercury methylation pathway in all methylating bacteria and archaea sequenced to date.

Connecting network properties of rapidly disseminating epizoonotics.

BACKGROUND: To effectively control the geographical dissemination of infectious diseases, their properties need to be determined. To test that rapid microbial dispersal requires not only susceptible hosts but also a pre-existing, connecting network, we explored constructs meant to reveal the network properties associated with disease spread, which included the road structure. METHODS: Using geo-temporal data collected from epizoonotics in which all hosts were susceptible (mammals infected by Foot-and-mouth disease virus, Uruguay, 2001; birds infected by Avian Influenza virus H5N1, Nigeria, 2006), two models were compared: 1) 'connectivity', a model that integrated bio-physical concepts (the agent's transmission cycle, road topology) into indicators designed to measure networks ('nodes' or infected sites with short- and long-range links), and 2) 'contacts', which focused on infected individuals but did not assess connectivity. RESULTS: THE CONNECTIVITY MODEL SHOWED FIVE NETWORK PROPERTIES: 1) spatial aggregation of cases (disease clusters), 2) links among similar 'nodes' (assortativity), 3) simultaneous activation of similar nodes (synchronicity), 4) disease flows moving from highly to poorly connected nodes (directionality), and 5) a few nodes accounting for most cases (a "20:80" pattern). In both epizoonotics, 1) not all primary cases were connected but at least one primary case was connected, 2) highly connected, small areas (nodes) accounted for most cases, 3) several classes of nodes were distinguished, and 4) the contact model, which assumed all primary cases were identical, captured half the number of cases identified by the connectivity model. When assessed together, the synchronicity and directionality properties explained when and where an infectious disease spreads. CONCLUSIONS: Geo-temporal constructs of Network Theory's nodes and links were retrospectively validated in rapidly disseminating infectious diseases. They distinguished classes of cases, nodes, and networks, generating information usable to revise theory and optimize control measures. Prospective studies that consider pre-outbreak predictors, such as connecting networks, are recommended.

Nanoparticle Network Formation in Nanostructured and Disordered Block Copolymer Matrices.

Incorporation of nanoparticles composed of surface-functionalized fumed silica (FS) or native colloidal silica (CS) into a nanostructured block copolymer yields hybrid nanocomposites whose mechanical properties can be tuned by nanoparticle concentration and surface chemistry. In this work, dynamic rheology is used to probe the frequency and thermal responses of nanocomposites composed of a symmetric poly(styrene-b-methyl methacrylate) (SM) diblock copolymer and varying in nanoparticle concentration and surface functionality. At sufficiently high loading levels, FS nanoparticle aggregates establish a load-bearing colloidal network within the copolymer matrix. Transmission electron microscopy images reveal the morphological characteristics of the nanocomposites under these conditions.

Molecularly asymmetric triblock copolymers as a single-molecule route to ordered bidisperse polymer brushes.

The conditions signaling the formation of bidisperse brushes in ordered block copolymers are investigated as an A(2) block is progressively grown onto an A(1)B diblock copolymer to form a series of molecularly asymmetric, isomorphic A(1)BA(2) triblock copolymers. Small-angle scattering and self-consistent field theory confirm that the microphase-ordered period decreases when the A(2) block is short relative to the A(1) block, but then increases as A(1)+A(2) bidisperse brushes develop. The mechanical properties systematically follow the spatial distribution of the A(2) block.