Polarization Transfer in Inelastic Proton Scattering from 12-C and 16-O

This research was sponsored by the National Science Foundation Grant NSF PHY 87-1440

Atomic Parity Nonconservation: Electroweak Parameters and Nuclear Structure

There have been suggestions to measure atomic parity nonconservation (PNC) along an isotopic chain, by taking ratios of observables in order to cancel complicated atomic structure effects. Precise atomic PNC measurements could make a significant contribution to tests of the Standard Model at the level of one loop radiative corrections. However, the results also depend upon certain features of nuclear structure, such as the spatial distribution of neutrons in the nucleus. To examine the sensitivity to nuclear structure, we consider the case of Pb isotopes using various recent relativistic and non-relativistic nuclear model calculations. Contributions from nucleon internal weak structure are included, but found to be fairly negligible. The spread among present models in predicted sizes of nuclear structure effects may preclude using Pb isotope ratios to test the Standard Model at better than a one percent level, unless there are adequate independent tests of the nuclear models by various alternative strong and electroweak nuclear probes. On the other hand, sufficiently accurate atomic PNC experiments would provide a unique method to measure neutron distributions in heavy nuclei.Comment: 44 pages, INT Preprint DOE/ER/40561-050-INT92-00-1

Parity Violating Measurements of Neutron Densities

Parity violating electron nucleus scattering is a clean and powerful tool for measuring the spatial distributions of neutrons in nuclei with unprecedented accuracy. Parity violation arises from the interference of electromagnetic and weak neutral amplitudes, and the $Z^0$ of the Standard Model couples primarily to neutrons at low $Q^2$. The data can be interpreted with as much confidence as electromagnetic scattering. After briefly reviewing the present theoretical and experimental knowledge of neutron densities, we discuss possible parity violation measurements, their theoretical interpretation, and applications. The experiments are feasible at existing facilities. We show that theoretical corrections are either small or well understood, which makes the interpretation clean. The quantitative relationship to atomic parity nonconservation observables is examined, and we show that the electron scattering asymmetries can be directly applied to atomic PNC because the observables have approximately the same dependence on nuclear shape.Comment: 38 pages, 7 ps figures, very minor changes, submitted to Phys. Rev.

Microscopic calculations of medium effects for 200-MeV (p,p') reactions

We examine the quality of a G-matrix calculation of the effective nucleon-nucleon (NN) interaction for the prediction of the cross section and analyzing power for 200-MeV (p,p') reactions that populate natural parity states in $^{16}$O, $^{28}$Si, and $^{40}$Ca. This calculation is based on a one-boson-exchange model of the free NN force that reproduces NN observables well. The G-matrix includes the effects of Pauli blocking, nuclear binding, and strong relativistic mean-field potentials. The implications of adjustments to the effective mass ansatz to improve the quality of the approximation at momenta above the Fermi level will be discussed, along with the general quality of agreement to a variety of (p,p') transitions.Comment: 36 pages, TeX, 18 figure

Mucopolysaccharidosis type IIIB may predominantly present with an attenuated clinical phenotype

Mucopolysaccharidosis type IIIB (MPS IIIB, Sanfilippo syndrome type B) is a lysosomal storage disorder caused by deficiency of the enzyme N-acetyl-α-D-glucosaminidase (NAGLU). Information on the natural course of MPS IIIB is scarce but much needed in view of emerging therapies. To improve knowledge on the natural course, data on all 52 MPS IIIB patients ever identified by enzymatic studies in the Netherlands were gathered. Clinical data on 44 patients could be retrieved. Only a small number (n = 9; 21%) presented with a classical MPS III phenotype; all other patients showed a much more attenuated course of the disease characterized by a significantly slower regression of intellectual and motor abilities. The majority of patients lived well into adulthood. First signs of the disease, usually mild developmental delay, were observed at a median age of 4 years. Subsequently, patients showed a slowing and eventually a stagnation of development. Patients with the attenuated phenotype had a stable intellectual disability for many years. Molecular analysis was performed in 24 index patients. The missense changes p.R643C, p.S612G, p.E634K, and p.L497V were exclusively found in patients with the attenuated phenotype. MPS IIIB comprises a remarkably wide spectrum of disease severity, and an unselected cohort including all Dutch patients showed a large proportion (79%) with an attenuated phenotype. MPS IIIB must be considered in patients with a developmental delay, even in the absence of a progressive decline in intellectual abilities. A key feature, necessitating metabolic studies, is the coexistence of behavioral problems

SARS-CoV-2 variant Alpha has a spike-dependent replication advantage over the ancestral B.1 strain in human cells with low ACE2 expression

Epidemiological data demonstrate that Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) variants of concern (VOCs) Alpha and Delta are more transmissible, infectious, and pathogenic than previous variants. Phenotypic properties of VOC remain understudied. Here, we provide an extensive functional study of VOC Alpha replication and cell entry phenotypes assisted by reverse genetics, mutational mapping of spike in lentiviral pseudotypes, viral and cellular gene expression studies, and infectivity stability assays in an enhanced range of cell and epithelial culture models. In almost all models, VOC Alpha spread less or equally efficiently as ancestral (B.1) SARS-CoV-2. B.1. and VOC Alpha shared similar susceptibility to serum neutralization. Despite increased relative abundance of specific sgRNAs in the context of VOC Alpha infection, immune gene expression in infected cells did not differ between VOC Alpha and B.1. However, inferior spreading and entry efficiencies of VOC Alpha corresponded to lower abundance of proteolytically cleaved spike products presumably linked to the T716I mutation. In addition, we identified a bronchial cell line, NCI-H1299, which supported 24-fold increased growth of VOC Alpha and is to our knowledge the only cell line to recapitulate the fitness advantage of VOC Alpha compared to B.1. Interestingly, also VOC Delta showed a strong (595-fold) fitness advantage over B.1 in these cells. Comparative analysis of chimeric viruses expressing VOC Alpha spike in the backbone of B.1, and vice versa, showed that the specific replication phenotype of VOC Alpha in NCI-H1299 cells is largely determined by its spike protein. Despite undetectable ACE2 protein expression in NCI-H1299 cells, CRISPR/Cas9 knock-out and antibody-mediated blocking experiments revealed that multicycle spread of B.1 and VOC Alpha required ACE2 expression. Interestingly, entry of VOC Alpha, as opposed to B.1 virions, was largely unaffected by treatment with exogenous trypsin or saliva prior to infection, suggesting enhanced resistance of VOC Alpha spike to premature proteolytic cleavage in the extracellular environment of the human respiratory tract. This property may result in delayed degradation of VOC Alpha particle infectivity in conditions typical of mucosal fluids of the upper respiratory tract that may be recapitulated in NCI-H1299 cells closer than in highly ACE2-expressing cell lines and models. Our study highlights the importance of cell model evaluation and comparison for in-depth characterization of virus variant-specific phenotypes and uncovers a fine-tuned interrelationship between VOC Alpha- and host cell-specific determinants that may underlie the increased and prolonged virus shedding detected in patients infected with VOC Alpha

A Scalable System for Production of Functional Pancreatic Progenitors from Human Embryonic Stem Cells

Development of a human embryonic stem cell (hESC)-based therapy for type 1 diabetes will require the translation of proof-of-principle concepts into a scalable, controlled, and regulated cell manufacturing process. We have previously demonstrated that hESC can be directed to differentiate into pancreatic progenitors that mature into functional glucose-responsive, insulin-secreting cells in vivo. In this study we describe hESC expansion and banking methods and a suspension-based differentiation system, which together underpin an integrated scalable manufacturing process for producing pancreatic progenitors. This system has been optimized for the CyT49 cell line. Accordingly, qualified large-scale single-cell master and working cGMP cell banks of CyT49 have been generated to provide a virtually unlimited starting resource for manufacturing. Upon thaw from these banks, we expanded CyT49 for two weeks in an adherent culture format that achieves 50–100 fold expansion per week. Undifferentiated CyT49 were then aggregated into clusters in dynamic rotational suspension culture, followed by differentiation en masse for two weeks with a four-stage protocol. Numerous scaled differentiation runs generated reproducible and defined population compositions highly enriched for pancreatic cell lineages, as shown by examining mRNA expression at each stage of differentiation and flow cytometry of the final population. Islet-like tissue containing glucose-responsive, insulin-secreting cells was generated upon implantation into mice. By four- to five-months post-engraftment, mature neo-pancreatic tissue was sufficient to protect against streptozotocin (STZ)-induced hyperglycemia. In summary, we have developed a tractable manufacturing process for the generation of functional pancreatic progenitors from hESC on a scale amenable to clinical entry

Bioreactors as engineering support to treat cardiac muscle and vascular disease

Cardiovascular disease is the leading cause of morbidity and mortality in the Western World. The inability of fully differentiated, load-bearing cardiovascular tissues to in vivo regenerate and the limitations of the current treatment therapies greatly motivate the efforts of cardiovascular tissue engineering to become an effective clinical strategy for injured heart and vessels. For the effective production of organized and functional cardiovascular engineered constructs in vitro, a suitable dynamic environment is essential, and can be achieved and maintained within bioreactors. Bioreactors are technological devices that, while monitoring and controlling the culture environment and stimulating the construct, attempt to mimic the physiological milieu. In this study, a review of the current state of the art of bioreactor solutions for cardiovascular tissue engineering is presented, with emphasis on bioreactors and biophysical stimuli adopted for investigating the mechanisms influencing cardiovascular tissue development, and for eventually generating suitable cardiovascular tissue replacements

Pharmacological inhibition of bromodomain and extra-terminal proteins induces an NRF-2-mediated antiviral state that is subverted by SARS-CoV-2 infection

Inhibitors of bromodomain and extra-terminal proteins (iBETs), including JQ-1, have been suggested as potential prophylactics against SARS-CoV-2 infection. However, molecular mechanisms underlying JQ-1-mediated antiviral activity and its susceptibility to viral subversion remain incompletely understood. Pretreatment of cells with iBETs inhibited infection by SARS-CoV-2 variants and SARS-CoV, but not MERS-CoV. The antiviral activity manifested itself by reduced reporter expression of recombinant viruses, and reduced viral RNA quantities and infectious titers in the culture supernatant. While we confirmed JQ-1-mediated downregulation of expression of angiotensin-converting enzyme 2 (ACE2) and interferon-stimulated genes (ISGs), multi-omics analysis addressing the chromatin accessibility, transcriptome and proteome uncovered induction of an antiviral nuclear factor erythroid 2-related factor 2 (NRF-2)-mediated cytoprotective response as an additional mechanism through which JQ-1 inhibits SARS-CoV-2 replication. Pharmacological inhibition of NRF-2, and knockdown of NRF-2 and its target genes reduced JQ-1-mediated inhibition of SARS-CoV-2 replication. Serial passaging of SARS-CoV-2 in the presence of JQ-1 resulted in predominance of ORF6-deficient variant, which exhibited resistance to JQ-1 and increased sensitivity to exogenously administered type I interferon (IFN-I), suggesting a minimised need for SARS-CoV-2 ORF6-mediated repression of IFN signalling in the presence of JQ-1. Importantly, JQ-1 exhibited a transient antiviral activity when administered prophylactically in human airway bronchial epithelial cells (hBAECs), which was gradually subverted by SARS-CoV-2, and no antiviral activity when administered therapeutically following an established infection. We propose that JQ-1 exerts pleiotropic effects that collectively induce an antiviral state in the host, which is ultimately nullified by SARS-CoV-2 infection, raising questions about the clinical suitability of the iBETs in the context of COVID-19