Evaluation of concentrated space solar arrays using computer modeling

A general approach is developed for predicting the power output of a concentrator enhanced photovoltaic space array. A ray trace routine determines the concentrator intensity arriving at each solar cell. An iterative calculation determines the cell's operating temperature since cell temperature and cell efficiency are functions of one another. The end result of the iterative calculation is that the individual cell's power output is determined as a function of temperature and intensity. Circuit output is predicted by combining the individual cell outputs using the single diode model of a solar cell. Concentrated array characteristics such as uniformity of intensity and operating temperature at various points across the array are examined using computer modeling techniques. An illustrative example is given showing how the output of an array can be enhanced using solar concentration techniques

Beyond Tryptophan Synthase: Identification of Genes That Contribute to Chlamydia trachomatis Survival during Gamma Interferon-Induced Persistence and Reactivation

Chlamydia trachomatis can enter a viable but nonculturable state in vitro termed persistence. A common feature of C. trachomatis persistence models is that reticulate bodies fail to divide and make few infectious progeny until the persistence-inducing stressor is removed. One model of persistence that has relevance to human disease involves tryptophan limitation mediated by the host enzyme indoleamine 2,3-dioxygenase, which converts l-tryptophan to N-formylkynurenine. Genital C. trachomatis strains can counter tryptophan limitation because they encode a tryptophan-synthesizing enzyme. Tryptophan synthase is the only enzyme that has been confirmed to play a role in interferon gamma (IFN-γ)-induced persistence, although profound changes in chlamydial physiology and gene expression occur in the presence of persistence-inducing stressors. Thus, we screened a population of mutagenized C. trachomatis strains for mutants that failed to reactivate from IFN-γ-induced persistence. Six mutants were identified, and the mutations linked to the persistence phenotype in three of these were successfully mapped. One mutant had a missense mutation in tryptophan synthase; however, this mutant behaved differently from previously described synthase null mutants. Two hypothetical genes of unknown function, ctl0225 and ctl0694, were also identified and may be involved in amino acid transport and DNA damage repair, respectively. Our results indicate that C. trachomatis utilizes functionally diverse genes to mediate survival during and reactivation from persistence in HeLa cells

Interrogating Genes That Mediate Chlamydia trachomatis Survival in Cell Culture Using Conditional Mutants and Recombination

Intracellular bacterial pathogens in the family Chlamydiaceae are causes of human blindness, sexually transmitted disease, and pneumonia. Genetic dissection of the mechanisms of chlamydial pathogenicity has been hindered by multiple limitations, including the inability to inactivate genes that would prevent the production of elementary bodies. Many genes are also Chlamydia-specific genes, and chlamydial genomes have undergone extensive reductive evolution, so functions often cannot be inferred from homologs in other organisms. Conditional mutants have been used to study essential genes of many microorganisms, so we screened a library of 4,184 ethyl methanesulfonate-mutagenized Chlamydia trachomatis isolates for temperature-sensitive (TS) mutants that developed normally at physiological temperature (37°C) but not at nonphysiological temperatures. Heat-sensitive TS mutants were identified at a high frequency, while cold-sensitive mutants were less common. Twelve TS mutants were mapped using a novel markerless recombination approach, PCR, and genome sequencing. TS alleles of genes that play essential roles in other bacteria and chlamydia-specific open reading frames (ORFs) of unknown function were identified. Temperature-shift assays determined that phenotypes of the mutants manifested at distinct points in the developmental cycle. Genome sequencing of a larger population of TS mutants also revealed that the screen had not reached saturation. In summary, we describe the first approach for studying essential chlamydial genes and broadly applicable strategies for genetic mapping in Chlamydia spp. and mutants that both define checkpoints and provide insights into the biology of the chlamydial developmental cycle. IMPORTANCE: Study of the pathogenesis of Chlamydia spp. has historically been hampered by a lack of genetic tools. Although there has been recent progress in chlamydial genetics, the existing approaches have limitations for the study of the genes that mediate growth of these organisms in cell culture. We used a genetic screen to identify conditional Chlamydia mutants and then mapped these alleles using a broadly applicable recombination strategy. Phenotypes of the mutants provide fundamental insights into unexplored areas of chlamydial pathogenesis and intracellular biology. Finally, the reagents and approaches we describe are powerful resources for the investigation of these organisms

Amoxicillin-Clavulanate-Induced Liver Injury

Background and Aims Amoxicillin–clavulanate (AC) is the most frequent cause of idiosyncratic drug-induced injury (DILI) in the US DILI Network (DILIN) registry. Here, we examined a large cohort of AC-DILI cases and compared features of AC-DILI to those of other drugs. Methods Subjects with suspected DILI were enrolled prospectively, and cases were adjudicated as previously described. Clinical variables and outcomes of patients with AC-DILI were compared to the overall DILIN cohort and to DILI caused by other antimicrobials. Results One hundred and seventeen subjects with AC-DILI were identified from the cohort (n = 1038) representing 11 % of all cases and 24 % of those due to antimicrobial agents (n = 479). Those with AC-DILI were older (60 vs. 48 years, P < 0.001). AC-DILI was more frequent in men than women (62 vs. 39 %) compared to the overall cohort (40 vs. 60 %, P < 0.001). The mean time to symptom onset was 31 days. The Tb, ALT, and ALP were 7 mg/dL, 478, and 325 U/L at onset. Nearly all liver biopsies showed prominent cholestatic features. Resolution of AC-DILI, defined by return of Tb to <2.5 mg/dL, occurred on average 55 days after the peak value. Three female subjects required liver transplantation, and none died due to DILI. Conclusion AC-DILI causes a moderately severe, mixed hepatocellular–cholestatic injury, particularly in older men, unlike DILI in general, which predominates in women. Although often protracted, eventual apparent recovery is typical, particularly for men and usually in women, but three women required liver transplantation

Endothelin-1 enhances fibrogenic gene expression, but does not promote DNA synthesis or apoptosis in hepatic stellate cells

BACKGROUND: In liver injury, the pool of hepatic stellate cell (HSC) increases and produces extracellular matrix proteins, decreasing during the resolution of fibrosis. The profibrogenic role of endothelin-1 (ET-1) in liver fibrosis remains disputed. We therefore studied the effect of ET-1 on proliferation, apoptosis and profibrogenic gene expression of HSCs. RESULTS: First passage HSC predominantly expressed endothelin A receptor (ETAR) mRNA and 4th passage HSC predominantly expressed the endothelin B receptor (ETBR) mRNA. ET-1 had no effect on DNA synthesis in 1st passage HSC, but reduced DNA synthesis in 4th passage HSC by more than 50%. Inhibition of proliferation by endothelin-1 was abrogated by ETBR specific antagonist BQ788, indicating a prominent role of ETBR in growth inhibition. ET-1 did not prevent apoptosis induced by serum deprivation or Fas ligand in 1st or 4th passage HSC. However, ET-1 increased procollagen α1(I), transforming growth factor β-1 and matrix metalloproteinase (MMP)-2 mRNA transcripts in a concentration-dependent manner in 1st, but not in 4th passage HSC. Profibrogenic gene expression was abrogated by ETAR antagonist BQ123. Both BQ123 and BQ788 attenuated the increase of MMP-2 expression by ET-1. CONCLUSION: We show that ET-1 stimulates fibrogenic gene expression for 1st passage HSC and it inhibits HSC proliferation for 4th passage HSC. These data indicate the profibrogenic and antifibrogenic action of ET-1 for HSC are involved in the process of liver fibrosis

The Broad-Spectrum Antiviral Compound ST-669 Restricts Chlamydial Inclusion Development and Bacterial Growth and Localizes to Host Cell Lipid Droplets within Treated Cells

Novel broad-spectrum antimicrobials are a critical component of a strategy for combating antibiotic-resistant pathogens. In this study, we explored the activity of the broad-spectrum antiviral compound ST-669 for activity against different intracellular bacteria and began a characterization of its mechanism of antimicrobial action. ST-669 inhibits the growth of three different species of chlamydia and the intracellular bacterium Coxiella burnetii in Vero and HeLa cells but not in McCoy (murine) cells. The antichlamydial and anti-C. burnetii activity spectrum was consistent with those observed for tested viruses, suggesting a common mechanism of action. Cycloheximide treatment in the presence of ST-669 abrogated the inhibitory effect, demonstrating that eukaryotic protein synthesis is required for tested activity. Immunofluorescence microscopy demonstrated that different chlamydiae grow atypically in the presence of ST-669, in a manner that suggests the compound affects inclusion formation and organization. Microscopic analysis of cells treated with a fluorescent derivative of ST-669 demonstrated that the compound localized to host cell lipid droplets but not to other organelles or the host cytosol. These results demonstrate that ST-669 affects intracellular growth in a host-cell-dependent manner and interrupts proper development of chlamydial inclusions, possibly through a lipid droplet-dependent process

Psychologists’ Authenticity: Implications for Work in Professional and Therapeutic Settings

Derek J. Burks, PhD, is a licensed psychologist and postdoctoral psychology fellow at the Pacific Northwest Mental Illness Research, Education, and Clinical Center (MIRECC), located within the Veterans Affairs Medical Center in Portland, Oregon. He obtained his PhD in counseling psychology from the University of Oklahoma. His current research focuses on health disparities, posttraumatic stress disorder among sexual-minority U.S. military veterans, and culturally appropriate mental health treatment for American Indians.Yeshttps://us.sagepub.com/en-us/nam/manuscript-submission-guideline

Impaired dermal wound healing in discoidin domain receptor 2-deficient mice associated with defective extracellular matrix remodeling

Background The wounding response relies on tightly regulated crosstalk between recruited fibroblasts and the collagenous extracellular matrix (ECM). Discoidin domain receptor 2 (DDR2) is a tyrosine kinase receptor for fibrillar collagen expressed during pathologic scarring, for example wound healing, arthritis and cancer. We have previously shown that DDR2 phosphorylation drives key wounding responses in skin fibroblasts including proliferation, chemotactic migration and secretion of both metalloproteinases and fibrillar collagen. In this study we compared healing of cutaneous wounds in DDR2+/+ and DDR2-/- mice and analyzed specific fibroblast responses. Results Cutaneous wound healing was significantly delayed in DDR2-/- mice compared with DDR2+/+ animals. Reduced α-smooth muscle actin (αSMA) expression and matrix metalloproteinase 2 (MMP2) activity in the DDR2-/- wound extracts indicated defective recruitment of skin fibroblasts. DDR2-/- wounds showed decreased tensile strength during healing, which correlated with a significant reduction in collagen content and defective collagen crosslinking. Non-wounded skin in DDR2-/- mice expressed less mRNA of the crosslinking enzymes lysyl oxidase (LOX), lysyl hydroxylase1 (LH1) and matricellular 'secreted protein, acidic and rich in cysteine' (SPARC; also known as osteonectin). Skin fibroblasts isolated from DDR2-/- mice displayed altered mRNA expression of a cluster of collagens, proteoglycans, integrins and MMPs that have been previously correlated with DDR2 expression, and reduced LOX, LH1 and SPARC mRNA levels and proteins. Stable reconstitution of wild-type DDR2 by retroviral infection restored LOX, LH1 and SPARC mRNA and protein levels in DDR2-/- fibroblasts. Contraction of collagen gels was reduced in DDR2-/- fibroblasts, accompanied by significantly reduced phosphorylated SrcY418. Inhibition of either LOX activity by β-aminoproprionitrile or MMP activity by N-[(2R)-2-(hydroxamido carbonylmethyl)-4-methylpentanoyl]-l-tryptophan methylamide (GM6001) reduced collagen gel contraction by skin fibroblasts after DDR2 induction with soluble collagen type I. Conclusions DDR2 contributes to skin fibroblast responses during tissue injury. Defective synthesis of collagen type I, crosslinking molecules and MMP2 predispose DDR2-/- mice to defective dermal wounding

Predictive Power of Molecular Dynamics Receptor Structures in Virtual Screening

Molecular dynamics (MD) simulation is a well-established method for understanding protein dynamics. Conformations from unrestrained MD simulations have yet to be assessed for blind virtual screening (VS) by docking. This study presents a critical analysis of the predictive power of MD snapshots to this regard, evaluating two well-characterized systems of varying flexibility in ligand-bound and unbound configurations. Results from such VS predictions are discussed with respect to experimentally determined structures. In all cases, MD simulations provide snapshots that improve VS predictive power over known crystal structures, possibly due to sampling more relevant receptor conformations. Additionally, MD can move conformations previously not amenable to docking into the predictive range