Peroxisome Turnover and Diurnal Modulation of Antioxidant Activity in Retinal Pigment Epithelia Utilizes Microtubule-Associated Protein 1 Light Chain 3B (LC3B)

The retinal pigment epithelium (RPE) supports the outer retina through essential roles in the retinoid cycle, nutrient supply, ion exchange, and waste removal. Each day the RPE removes the oldest ∼10% of photoreceptor outer segment (OS) disk membranes through phagocytic uptake, which peaks following light onset. Impaired degradation of phagocytosed OS material by the RPE can lead to toxic accumulation of lipids, oxidative tissue damage, inflammation, and cell death. OSs are rich in very long chain fatty acids, which are preferentially catabolized in peroxisomes. Despite the importance of lipid degradation in RPE function, the regulation of peroxisome number and activity relative to diurnal OS ingestion is relatively unexplored. Using immunohistochemistry, immunoblot analysis, and catalase activity assays, we investigated peroxisome abundance and activity at 6 AM, 7 AM (light onset), 8 AM, and 3 PM, in wild-type (WT) mice and mice lacking microtubule-associated protein 1 light chain 3B (Lc3b), which have impaired phagosome degradation. We found that catalase activity, but not the amount of catalase protein, is 50% higher in the morning compared with 3 PM, in RPE of WT, but not Lc3b-/-, mice. Surprisingly, we found that peroxisome abundance was stable during the day in RPE of WT mice; however, numbers were elevated overall in Lc3b-/- mice, implicating LC3B in autophagic organelle turnover in RPE. Our data suggest that RPE peroxisome function is regulated in coordination with phagocytosis, possibly through direct enzyme regulation, and may serve to prepare RPE peroxisomes for daily surges in ingested lipid-rich OS. Copyright © 2019 the American Physiological Society

Social Workers' Attitudes Towards Public Accountability

The public demand for accountability of human services has been increasing in the United States. Despite the growing importance of public accountability as a special responsibility of social workers, little information is available in U.S. on how these pro fessionals react to the implementation of accountability programs. The survey reported in this paper was made to explore the attitudes of social workers in U.S. hospitals toward PSRO, a nationwide health care service review system. The paper presents a descriptive overview of significant aspects of American social workers' personal attitudes toward various issues of current concern about this accountability system.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/67090/2/10.1177_002087288402700307.pd

Three-dimensional organization of nascent rod outer segment disk membranes

The vertebrate photoreceptor cell contains an elaborate cilium that includes a stack of phototransductive membrane disks. The disk membranes are continually renewed, but how new disks are formed remains poorly understood. Here we used electron microscope tomography to obtain 3D visualization of the nascent disks of rod photoreceptors in three mammalian species, to gain insight into the process of disk morphogenesis. We observed that nascent disks are invariably continuous with the ciliary plasma membrane, although, owing to partial enclosure, they can appear to be internal in 2D profiles. Tomographic analyses of the basal-most region of the outer segment show changes in shape of the ciliary plasma membrane indicating an invagination, which is likely a first step in disk formation. The invagination flattens to create the proximal surface of an evaginating lamella, as well as membrane protrusions that extend between adjacent lamellae, thereby initiating a disk rim. Immediately distal to this initiation site, lamellae of increasing diameter are evident, indicating growth outward from the cilium. In agreement with a previous model, our data indicate that mature disks are formed once lamellae reach full diameter, and the growth of a rim encloses the space between adjacent surfaces of two lamellae. This study provides 3D data of nascent and mature rod photoreceptor disk membranes at unprecedented z-axis depth and resolution, and provides a basis for addressing fundamental questions, ranging from protein sorting in the photoreceptor cilium to photoreceptor electrophysiology

Ammonium Toxicity and Potassium Limitation in Yeast

DNA microarray analysis of gene expression in steady-state chemostat cultures limited for potassium revealed a surprising connection between potassium and ammonium: potassium limits growth only when ammonium is the nitrogen source. Under potassium limitation, ammonium appears to be toxic for Saccharomyces cerevisiae. This ammonium toxicity, which appears to occur by leakage of ammonium through potassium channels, is recapitulated under high-potassium conditions by over-expression of ammonium transporters. Although ammonium toxicity is well established in metazoans, it has never been reported for yeast. To characterize the response to ammonium toxicity, we examined the filtrates of these cultures for compounds whose excretion might serve to detoxify the ammonium (such as urea in mammals). Using liquid chromatography–tandem mass spectrometry to assay for a wide array of metabolites, we detected excreted amino acids. The amounts of amino acids excreted increased in relation to the severity of growth impairment by ammonium, suggesting that amino acid excretion is used by yeast for ammonium detoxification

Inefficient Quality Control of Thermosensitive Proteins on the Plasma Membrane

BACKGROUND: Misfolded proteins are generally recognised by cellular quality control machinery, which typically results in their ubiquitination and degradation. For soluble cytoplasmic proteins, degradation is mediated by the proteasome. Membrane proteins that fail to fold correctly are subject to ER associated degradation (ERAD), which involves their extraction from the membrane and subsequent proteasome-dependent destruction. Proteins with abnormal transmembrane domains can also be recognised in the Golgi or endosomal system and targeted for destruction in the vacuole/lysosome. It is much less clear what happens to membrane proteins that reach their destination, such as the cell surface, and then suffer damage. METHODOLOGY/PRINCIPAL FINDINGS: We have tested the ability of yeast cells to degrade membrane proteins to which temperature-sensitive cytoplasmic alleles of the Ura3 protein or of phage lambda repressor have been fused. In soluble form, these proteins are rapidly degraded upon temperature shift, in part due to the action of the Doa10 and San1 ubiquitin ligases and the proteasome. When tethered to the ER protein Use1, they are also degraded. However, when tethered to a plasma membrane protein such as Sso1 they escape degradation, either in the vacuole or by the proteasome. CONCLUSIONS/SIGNIFICANCE: Membrane proteins with a misfolded cytoplasmic domain appear not to be efficiently recognised and degraded once they have escaped the ER, even though their defective domains are exposed to the cytoplasm and potentially to cytoplasmic quality controls. Membrane tethering may provide a way to reduce degradation of unstable proteins

Interaction of the Deubiquitinating Enzyme Ubp2 and the E3 Ligase Rsp5 Is Required for Transporter/Receptor Sorting in the Multivesicular Body Pathway

Protein ubiquitination is essential for many events linked to intracellular protein trafficking. We sought to elucidate the possible involvement of the S. cerevisiae deubiquitinating enzyme Ubp2 in transporter and receptor trafficking after we (this study) and others established that affinity purified Ubp2 interacts stably with the E3 ubiquitin ligase Rsp5 and the (ubiquitin associated) UBA domain containing protein Rup1. UBP2 interacts genetically with RSP5, while Rup1 facilitates the tethering of Ubp2 to Rsp5 via a PPPSY motif. Using the uracil permease Fur4 as a model reporter system, we establish a role for Ubp2 in membrane protein turnover. Similar to hypomorphic rsp5 alleles, cells deleted for UBP2 exhibited a temporal stabilization of Fur4 at the plasma membrane, indicative of perturbed protein trafficking. This defect was ubiquitin dependent, as a Fur4 N-terminal ubiquitin fusion construct bypassed the block and restored sorting in the mutant. Moreover, the defect was absent in conditions where recycling was absent, implicating Ubp2 in sorting at the multivesicular body. Taken together, our data suggest a previously overlooked role for Ubp2 as a positive regulator of Rsp5-mediated membrane protein trafficking subsequent to endocytosis

A critical review of the research literature on Six Sigma, Lean and StuderGroup's Hardwiring Excellence in the United States: the need to demonstrate and communicate the effectiveness of transformation strategies in healthcare

<p>Abstract</p> <p>Background</p> <p>U.S. healthcare organizations are confronted with numerous and varied transformational strategies promising improvements along all dimensions of quality and performance. This article examines the peer-reviewed literature from the U.S. for evidence of effectiveness among three current popular transformational strategies: Six Sigma, Lean/Toyota Production System, and Studer's Hardwiring Excellence.</p> <p>Methods</p> <p>The English language health, healthcare management, and organizational science literature (up to December 2007) indexed in Medline, Web of Science, ABI/Inform, Cochrane Library, CINAHL, and ERIC was reviewed for studies on the aforementioned transformation strategies in healthcare settings. Articles were included if they: appeared in a peer-reviewed journal; described a specific intervention; were not classified as a pilot study; provided quantitative data; and were not review articles. Nine references on Six Sigma, nine on Lean/Toyota Production System, and one on StuderGroup meet the study's eligibility criteria.</p> <p>Results</p> <p>The reviewed studies universally concluded the implementations of these transformation strategies were successful in improving a variety of healthcare related processes and outcomes. Additionally, the existing literature reflects a wide application of these transformation strategies in terms of both settings and problems. However, despite these positive features, the vast majority had methodological limitations that might undermine the validity of the results. Common features included: weak study designs, inappropriate analyses, and failures to rule out alternative hypotheses. Furthermore, frequently absent was any attention to changes in organizational culture or substantial evidence of lasting effects from these efforts.</p> <p>Conclusion</p> <p>Despite the current popularity of these strategies, few studies meet the inclusion criteria for this review. Furthermore, each could have been improved substantially in order to ensure the validity of the conclusions, demonstrate sustainability, investigate changes in organizational culture, or even how one strategy interfaced with other concurrent and subsequent transformation efforts. While informative results can be gleaned from less rigorous studies, improved design and analysis can more effectively guide healthcare leaders who are motivated to transform their organizations and convince others of the need to employ such strategies. Demanding more exacting evaluation of projects consultants, or partnerships with health management researchers in academic settings, can support such efforts.</p

Specificity of Transmembrane Protein Palmitoylation in Yeast

Many proteins are modified after their synthesis, by the addition of a lipid molecule to one or more cysteine residues, through a thioester bond. This modification is called S-acylation, and more commonly palmitoylation. This reaction is carried out by a family of enzymes, called palmitoyltransferases (PATs), characterized by the presence of a conserved 50- aminoacids domain called “Asp-His-His-Cys- Cysteine Rich Domain” (DHHC-CRD). There are 7 members of this family in the yeast Saccharomyces cerevisiae, and each of these proteins is thought to be responsible for the palmitoylation of a subset of substrates. Substrate specificity of PATs, however, is not yet fully understood. Several yeast PATs seem to have overlapping specificity, and it has been proposed that the machinery responsible for palmitoylating peripheral membrane proteins in mammalian cells, lacks specificity altogether

Parametric analysis of nightside conductance effects on inner magnetospheric dynamics for the 17 April 2002 storm

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95027/1/jgra17945.pd