The expression and metabolism of low density lipoprotein receptors in familial hypercholesterolaemia

The expression of two phenotypically-contrasting LDL receptor mutations was characterized in cultured fibroblasts from the genetically-homozygous Afrikaner subjects, FH1a and lb, and FH3a and 3b, respectively. Surface receptor expression and functional activity were studied by ligand (¹²⁵I-LDL) and monoclonal antibody (¹²⁵I-IgG-C7) binding, and c35s]-methionine pulse-chase experiments were used to analyze biosynthesis, processing and degradation of IgG-C7- immunoprecipitable mutant receptors. Cells from the "receptor-negative" subjects, FH3a and 3b exhibited reduced, but significant (40-60% of normal) LDL receptor synthesis rates. Newly-synthesized precursors were processed slowly (t½ 1.5 hours versus normal t½ of approximately 15 minutes) to mature receptors which reached the cell-surface, but were rapidly degraded thereafter with a half-life of approximately 1.7 hours (normal value 12.6 hours) thus representing a new type of LDL receptor defect. Lysosomotropic weak bases such as ammonium chloride partially inhibited rapid degradation of the mutant receptors, suggesting the involvement of proteolysis in acidic compartments such as lysosomes or endosomes. Fibroblasts from FH1a and lb exhibited normal synthesis rates of LDL receptor precursors that were processed at a severely reduced rate (t½ approximately 5 hours) to functionally heterogeneous mature surface receptors. Onethird of the receptors (20% of normal levels) bound ¹²⁵I-LDL with normal affinity at 4°C and 37°C, whereas the majority were able to recognize only ¹²⁵I-IgG-C7, and apparently showed defective internalisation and subsequent degradation of the bound IgG-C7 at 37°C. The existence of the two receptor populations was further supported by selective intracellular trapping and degradation of only the active, LDL-binding population, in the presence of ammonium chloride and LOL. The abnormal form predominated even in newly-synthesized receptors and reached a maximum of 50-70% of normal levels after 48 hours of upregulation. Upregulation kinetics and degradation rates (t½ = 10-11 hours) of both functionally-active and abnormal receptor populations were similar to normal. A progressive increase in apparent molecular weight of the slowly-processed precursor receptors suggested a possible role for abnormal glycosylation in the formation of both "normal" and abnormal conformations of the same receptor molecule

SANBI and BHL-Africa: preserving biodiversity literature

Biodiversity Heritage Library.Abstract The Biodiversity Heritage Library is a consortium of natural history and botanical libraries that digitise and make accessible the biodiversity literature held in collections and also literature available open access. Published literature on biological diversity has limited global distribution; much of it is available in only a few select libraries, yet literature about the biota existing in developing countries is often not available within their own borders. Access to published literature is one of the chief obstacles to research. The BHL consortium works with the international taxonomic community to ensure that biodiversity heritage is made available to a global audience through open access. BHL members digitise public domain books and journals and obtain permission from publishers for materials still under copyright. In partnership with Internet Archive, taxonomic communities and local digitisation efforts, BHL has digitised almost 40 million pages of scientific literature. BHL provides a range of services and APIs which allow users to harvest data files, species information and reuse content for research purposes. Since 2009, BHL has expanded and gBHL (global biodiversity heritage library) is a network of autonomous members operating programs and projects to make biodiversity literature. They are: BHL-Europe Chinese Academy of Sciences Atlas of Living Australia Brazil (through SciELO) Bibliotheca Alexandrina Coming soon is BHL Africa BHL Africa is an inclusive network of African libraries and institutions in Western, Eastern, Central and Southern Africa. BHL Africa’s guiding principles and values are: Open Access, Collaboration and Transparency. SANBI is legally mandated to manage biodiversity information. The Biodiversity Information Management Directorate (BIM) is responsible for the effective management of information and such information can be accessed through the Biodiversity Advisor http://biodiversityadvisor.sanbi.org As the leading biodiversity institute in Africa, SANBI Libraries has been given the task to officially launch BHL Africa in April 2013

Cytosolic thioredoxin reductase 1 is required for correct disulfide formation in the ER

Folding of proteins entering the secretory pathway in mammalian cells frequently requires the insertion of disulfide bonds. Disulfide insertion can result in covalent linkages found in the native structure as well as those that are not, so‐called non‐native disulfides. The pathways for disulfide formation are well characterized, but our understanding of how non‐native disulfides are reduced so that the correct or native disulfides can form is poor. Here, we use a novel assay to demonstrate that the reduction in non‐native disulfides requires NADPH as the ultimate electron donor, and a robust cytosolic thioredoxin system, driven by thioredoxin reductase 1 (TrxR1 or TXNRD1). Inhibition of this reductive pathway prevents the correct folding and secretion of proteins that are known to form non‐native disulfides during their folding. Hence, we have shown for the first time that mammalian cells have a pathway for transferring reducing equivalents from the cytosol to the ER, which is required to ensure correct disulfide formation in proteins entering the secretory pathway

Intramedullary spinal masses : a pictorial essay

CITATION: Bezuidenhout, A.F., Lipsitz, J.M., Du Plessis, A. 2014. Intramedullary spinal masses: a pictorial essay. South African Journal of Radiology, 18(1):1-7, doi: 10.4102/sajr.v18i1.602.The original publication is available at http://www.sajr.org.za/index.php/sajrThis pictorial essay provides a classification system for the most common intramedullary spinal masses and describes distinguishing imaging features that will aid the radiologist in providing a relevant differential diagnosis to guide further management.http://www.sajr.org.za/index.php/sajr/article/view/602Publisher's versio

The use of confocal microscopy in quantifying changes in membrane potential

Monitoring the plasma membrane potential and its changes can be a time consuming and challenging task especially when conventional electrophysiological techniques are used. The use of potentiometric fluorophores, namely tetramethylrhodamine methylester (TMRM), and digital imaging devices (laser scanning confocal microscopy) provides reliable and time efficient method. Two scorpion pore-forming peptides, namely PP and OP1, were used as a tool to induce depolarization of the plasma membrane potential of neuroblastoma cell line and cardiac myocytes. Alternative methods for the neuroblastoma cells and cardiac myocytes were used. Depolarization of the neuroblastoma cells was calibrated with 140 mM KCl solution with 1 µM valinomycin, after which intensity readers were substituted in the Nernst equation for quantification. Calibration of the alternative method used of the cardiac myocytes' plasma membrane potential changes was calibrated with the use of 5, 20, 40, and 80 mM KCl solutions with 1 µM valinomycin. A calibration curve was then constructed from which plasma membrane potential could be calculated

Community Engagement newsletter, Faculty of Veterinary Science, Summer, 2012

Originally published as HTML file, converted to PDF with Adobe Acrobat 9 Pro Version 9.0.0.Visiting Mamelodi schools / Anne Schantz -- The presence of toxic plants in zoo enclosures and their effect on herbivores within these enclosures / Gillian Declercq, Shreya Venkatkumar, Storm van Tonder and Thandi Fourie -- Isuzu Vet Books for Africa … will the dream become a reality? / Ben Mullerab201

Pharmacologic modulation of RORγt translates to efficacy in preclinical and translational models of psoriasis and inflammatory arthritis.

The IL-23/IL-17 pathway is implicated in autoimmune diseases, particularly psoriasis, where biologics targeting IL-23 and IL-17 have shown significant clinical efficacy. Retinoid-related orphan nuclear receptor gamma t (RORγt) is required for Th17 differentiation and IL-17 production in adaptive and innate immune cells. We identified JNJ-54271074, a potent and highly-selective RORγt inverse agonist, which dose-dependently inhibited RORγt-driven transcription, decreased co-activator binding and promoted interaction with co-repressor protein. This compound selectively blocked Th17 differentiation, significantly reduced IL-17A production from memory T cells, and decreased IL-17A- and IL-22-producing human and murine γδ and NKT cells. In a murine collagen-induced arthritis model, JNJ-54271074 dose-dependently suppressed joint inflammation. Furthermore, JNJ-54271074 suppressed IL-17A production in human PBMC from rheumatoid arthritis patients. RORγt-deficient mice showed decreased IL-23-induced psoriasis-like skin inflammation and cytokine gene expression, consistent with dose-dependent inhibition in wild-type mice through oral dosing of JNJ-54271074. In a translational model of human psoriatic epidermal cells and skin-homing T cells, JNJ-54271074 selectively inhibited streptococcus extract-induced IL-17A and IL-17F. JNJ-54271074 is thus a potent, selective RORγt modulator with therapeutic potential in IL-23/IL-17 mediated autoimmune diseases

Genomic analysis of focal nodular hyperplasia with associated hepatocellular carcinoma unveils its malignant potential: a case report.

Background Focal nodular hyperplasia (FNH) is typically considered a benign tumor of the liver without malignant potential. The co-occurrence of FNH and hepatocellular carcinoma (HCC) has been reported in rare cases. In this study we sought to investigate the clonal relationship between these lesions in a patient with FNH-HCC co-occurrence. Methods A 74-year-old female patient underwent liver tumor resection. The resected nodule was subjected to histologic analyses using hematoxylin and eosin stain and immunohistochemistry. DNA extracted from microdissected FNH and HCC regions was subjected to whole exome sequencing. Clonality analysis were performed using PyClone. Results Histologic analysis reveals that the nodule consists of an FNH and two adjoining HCC components with distinct histopathological features. Immunophenotypic characterization and genomic analyses suggest that the FNH is clonally related to the HCC components, and is composed of multiple clones at diagnosis, that are likely to have progressed to HCC through clonal selection and/or the acquisition of additional genetic events. Conclusion To the best of our knowledge, our work is the first study showing a clonal relationship between FNH and HCC. We show that FNH may possess the capability to undergo malignant transformation and to progress to HCC in very rare cases

Anti-Inflammatory Activity of a Potent, Selective Leukotriene A4 Hydrolase Inhibitor in Comparison with the 5-Lipoxygenase Inhibitor Zileuton

ABSTRACT Leukotriene A 4 hydrolase (LTA 4 H) catalyzes production of the proinflammatory lipid mediator, leukotriene (LT) B 4 , which is implicated in a number of inflammatory diseases. We have identified a potent and selective inhibitor of both the epoxide hydrolase and aminopeptidase activities of recombinant human LTA 4 H (IC 50 , approximately 10 nM). In a murine model of arachidonic acid-induced ear inflammation, the LTA 4 H inhibitor, JNJ-26993135 (1-[4-(benzothiazol-2-yloxy)-benzyl]-piperidine-4-carboxylic acid), dose-dependently inhibited ex vivo LTB 4 production in blood, in parallel with dose-dependent inhibition of neutrophil influx (ED 50 , 1-3 mg/kg) and ear edema. In murine whole blood and in zymosan-induced peritonitis, JNJ-26993135 selectively inhibited LTB 4 production, without affecting cysteinyl leukotriene production, while maintaining or increasing production of the anti-inflammatory mediator, lipoxin (LX) A 4 . The 5-lipoxygenase (5-LO) inhibitor zileuton showed inhibition of LTB 4 , LTC 4 , and LXA 4 production. Although zileuton inhibited LTB 4 production in the peritonitis model more effectively than the LTA 4 H inhibitor, the influx of neutrophils into the peritoneum after 1 and 2 h was significantly higher in zileuton-versus JNJ-26993135-treated animals. This difference may have been mediated by the increased LXA 4 levels in the presence of the LTA 4 H inhibitor. The selective inhibition of LTB 4 production by JNJ-26993135, while increasing levels of the anti-inflammatory mediator, LXA 4 , may translate to superior therapeutic efficacy versus 5-LO or 5-LO-activating protein inhibitors in LTB 4 -mediated inflammatory diseases