Metabolism of low-density lipoproteins by cultured hepatocytes from normal and homozygous familial hypercholesterolemic subjects

The profoundly elevated concentrations of low-density lipoproteins (LDL) present in homozygous familial hypercholesterolemia lead to symptomatic cardiovascular disease and death by early adulthood. Studies conducted in nonhepatic tissues demonstrated defective cellular recognition and metabolism of LDL in these patients. Since mammalian liver removes at least half of the LDL in the circulation, the metabolism of LDL by cultured hepatocytes isolated from familial hypercholesterolemic homozygotes was compared to hepatcytes from normal individuals. Fibroblast studies demonstrated that the familial hypercholesterolemic subjects studied were LDL receptor-negative (less than 1% normal receptor activity) and LDL receptor-de fective (18% normal receptor activity). Cholesterol-depleted hepatocytes from normal subjects bound and internalized 125I-labeled LDL (Bmax = 2.2 μg LDL/mg cell protein). Preincubation of normal hepatocytes with 200 μg/ml LDL reduced binding and internalization by approx. 40%. In contrast, 125I-labeled LDL binding and internalization by receptor-negative familial hypercholesterolemic hepatocytes was unaffected by cholesterol loading and considerably lower than normal. This residual LDL uptake could not be ascribed to fluid phase endocytosis as determined by [14C]sucrose uptake. The residual LDL binding by familial hypercholesterolemia hepatocytes led to a small increase in hepatocyte cholesterol content which was relatively ineffective in reducing hepatocyte 3-hydroxy-3-methylglutaryl-CoA reductase activity. Receptordefective familial hypercholesterolemia hepatocytes retained some degree of regulatable 125I-labeled LDL uptake, but LDL uptake did not lead to normal hepatocyte cholesterol content or 3-hydroxy-3-methylglutaryl-CoA reductase activity. These combined results indicate that the LDL receptor abnormality present in familial hypercholesterolemia fibroblasts reflects deranged hepatocyte LDL recognition and metabolism. In addition, a low-affinity, nonsaturable uptake process for LDL is present in human liver which does not efficiently modulate hepatocyte cholesterol content or synthesis. © 1986

Transport of apolipoproteins A-I and A-II by human thoracic duct lymph

The daily transport of human plasma apolipoproteins A-I and A-II, triglyceride, and total cholesterol from the thoracic duct lymph into plasma was measured in 2 subjects before and 3 subjects after renal transplantation. Lymph triglyceride transport was ~83% of the daily ingested fat loads, whereas lymph cholesterol transport was consistently greater than the amount of daily ingested cholesterol. Lymph apolipoprotein transport significantly (P < 0.05) exceeded the predicted apolipoprotein synthesis rate by an average of 659±578 mg/d for apolipoprotein A-I and 109±59 mg/d for apolipoprotein A-II among the 5 subjects. It is estimated that 22-77% (apolipoprotein A-I) and 28-82% (apolipoprotein A-II) of daily total body apolipoprotein synthesis takes place in the intestine. Lymph high density lipoprotein particles are mostly high density lipoprotein(2b) and high density lipoprotein(2a) and have a greater overall relative triglyceride content and a smaller relative cholesteryl ester content when compared with homologous plasma high density lipoproteins. The major quantity of both lymph apolipoprotein A-I (81±8%) and apolipoprotein A-II (90±11%) was found within high density lipoproteins with almost all of the remainder found in chylomicrons and very low density lipoproteins. The combined results are consistent with a major contribution of the intestine to total body synthesis of apolipoprotein A-I and apolipoprotein A-II. An important role of lymph in returning filtered apolipoprotein to plasma in association with high density lipoproteins is proposed. Accompanying the return of filtered apolipoprotein to the plasma is a probable transformation, both in size and composition, of at least some of the lymph high density lipoprotein(2b) and high density lipoprotein(2a) particles into high density lipoprotein3

Characterization of hepatic low density lipoprotein binding and cholesterol metabolism in normal and homozygous familial hypercholesterolemic subjects

Patients with familial hypercholesterolemia have elevated levels of plasma low density lipoproteins (LDL), increased hepatic synthesis of apolipoprotein B-containing lipoproteins, defective binding of low density lipoproteins to fibroblasts, and premature atherosclerosis. The role of a hepatic low density lipoprotein receptor in normal man and its importance in the pathogenesis of familial hypercholesterolemia have not been previously determined. In the present study, direct comparison was made of the binding of LDL to hepatic membranes from normal and receptor-negative homozygous familial hypercholesterolemic subjects. The effects of calcium, EDTA, and temperature on the binding of lipoproteins to the hepatic membranes were also evaluated. At 4°C, no significant difference in specific binding of LDL to hepatic membranes from normal and familial hypercholesterolemic subjects was observed. At 37°C, both total and specific binding of LDL were significantly reduced in patients with familial hypercholesterolemia. Hepatic membrane binding of LDL from the two patients homozygous for receptor-negative familial hypercholesterolemia was 53 and 59% of normal. The activity of the rate-limiting enzyme in cholesterol biosynthesis, 3-hydroxy-3-methylglutaryl coenzyme A reductase was normal; however, the total hepatic cholesterol and cholesteryl ester content was significantly increased from 53 to 129%. These results indicate that patients with familial hypercholesterolemia have a defect in the interaction of hepatic membranes with low density lipoproteins. This defect may lead to accelerated atherosclerosis by decreasing the cellular catabolism of LDL and enhancing the production of LDL, which is characteristic of patients homozygous for familial hypercholesterolemia

Differential Dopamine D1 and D3 Receptor Modulation and Expression in the Spinal Cord of Two Mouse Models of Restless Legs Syndrome

Restless Legs Syndrome (RLS) is often and successfully treated with dopamine receptor agonists that target the inhibitory D3 receptor subtype, however there is no clinical evidence of a D3 receptor dysfunction in RLS patients. In contrast, genome-wide association studies in RLS patients have established that a mutation of the MEIS1 gene is associated with an increased risk in developing RLS, but the effect of MEIS1 dysfunction on sensorimotor function remain unknown. Mouse models for a dysfunctional D3 receptor (D3KO) and Meis1 (Meis1KO) were developed independently, and each animal expresses some features associated with RLS in the clinic, but they have not been compared in their responsiveness to treatment options used in the clinic. We here confirm that D3KO and Meis1KO animals show increased locomotor activities, but that only D3KO show an increased sensory excitability to thermal stimuli. Next we compared the effects of dopaminergics and opioids in both animal models, and we assessed D1 and D3 dopamine receptor expression in the spinal cord, the gateway for sensorimotor processing. We found that Meis1KO share most of the tested behavioral properties with their wild type (WT) controls, including the modulation of the thermal pain withdrawal reflex by morphine, L-DOPA and D3 receptor (D3R) agonists and antagonists. However, Meis1KO and D3KO were behaviorally more similar to each other than to WT when tested with D1 receptor (D1R) agonists and antagonists. Subsequent Western blot analyses of D1R and D3R protein expression in the spinal cord revealed a significant increase in D1R but not D3R expression in Meis1KO and D3KO over WT controls. As the D3R is mostly present in the dorsal spinal cord where it has been shown to modulate sensory pathways, while activation of the D1Rs can activate motoneurons in the ventral spinal cord, we speculate that D3KO and Meis1KO represent two complementary animal models for RLS, in which the mechanisms of sensory (D3R-mediated) and motor (D1R-mediated) dysfunctions can be differentially explored

Market familiarity and the location of South and North MNEs

We use a systematic empirical analysis of the determinants of South-South (SS) and North-South (NS) foreign direct investment (FDI) as a canvas to explore how multinational enterprises’ (MNEs) location decisions are shaped by better acquaintance with a foreign market resulting from bilateral ties, experience of international expansion, and knowledge of how to deal with poor governance. We find that these various aspects of market familiarity, which can interact together, are important to explain and differentiate the location behaviors of South MNEs (S-MNEs) and North MNEs (N-MNEs) in developing countries

Psychological determinants of whole-body endurance performance

Background: No literature reviews have systematically identified and evaluated research on the psychological determinants of endurance performance, and sport psychology performance-enhancement guidelines for endurance sports are not founded on a systematic appraisal of endurance-specific research. Objective: A systematic literature review was conducted to identify practical psychological interventions that improve endurance performance and to identify additional psychological factors that affect endurance performance. Additional objectives were to evaluate the research practices of included studies, to suggest theoretical and applied implications, and to guide future research. Methods: Electronic databases, forward-citation searches, and manual searches of reference lists were used to locate relevant studies. Peer-reviewed studies were included when they chose an experimental or quasi-experimental research design, a psychological manipulation, endurance performance as the dependent variable, and athletes or physically-active, healthy adults as participants. Results: Consistent support was found for using imagery, self-talk, and goal setting to improve endurance performance, but it is unclear whether learning multiple psychological skills is more beneficial than learning one psychological skill. The results also demonstrated that mental fatigue undermines endurance performance, and verbal encouragement and head-to-head competition can have a beneficial effect. Interventions that influenced perception of effort consistently affected endurance performance. Conclusions: Psychological skills training could benefit an endurance athlete. Researchers are encouraged to compare different practical psychological interventions, to examine the effects of these interventions for athletes in competition, and to include a placebo control condition or an alternative control treatment. Researchers are also encouraged to explore additional psychological factors that could have a negative effect on endurance performance. Future research should include psychological mediating variables and moderating variables. Implications for theoretical explanations of endurance performance and evidence-based practice are described

Psychosocial factors associated with outcomes of sports injury rehabilitation in competitive athletes: a mixed studies systematic review.

The prime focus of research on sports injury has been on physical factors. This is despite our understanding that when an athlete sustains an injury it has psychosocial as well as physical impacts. Psychosocial factors have been suggested as prognostic influences on the outcomes of rehabilitation. The aim of this work was to address the question: are psychosocial factors associated with sports injury rehabilitation outcomes in competitive athletes?Mixed studies systematic review (PROSPERO reg.CRD42014008667).Electronic database and bibliographic searching was undertaken from the earliest entry until 1 June 2015. Studies that included injured competitive athletes, psychosocial factors and a sports injury rehabilitation outcome were reviewed by the authors. A quality appraisal of the studies was undertaken to establish the risk of reporting bias.25 studies were evaluated that included 942 injured competitive athletes were appraised and synthesised. Twenty studies had not been included in previous reviews. The mean methodological quality of the studies was 59% (moderate risk of reporting bias). Convergent thematic analysis uncovered three core themes across the studies: (1) emotion associated with rehabilitation outcomes; (2) cognitions associated with rehabilitation outcomes; and (3) behaviours associated with rehabilitation outcomes. Injury and performance-related fears, anxiety and confidence were associated with rehabilitation outcomes. There is gender-related, age-related and injury-related bias in the reviewed literature.Psychosocial factors were associated with a range of sports injury rehabilitation outcomes. Practitioners need to recognise that an injured athlete's thoughts, feelings and actions may influence the outcome of rehabilitation

eIF2α Kinases Regulate Development through the BzpR Transcription Factor in Dictyostelium discoideum

A major mechanism of translational regulation in response to a variety of stresses is mediated by phosphorylation of eIF2α to reduce delivery of initiator tRNAs to scanning ribosomes. For some mRNAs, often encoding a bZIP transcription factor, eIF2α phosphorylation leads to enhanced translation due to delayed reinitiation at upstream open reading frames. Dictyostelium cells possess at least three eIF2α kinases that regulate various portions of the starvation-induced developmental program. Cells possessing an eIF2α that cannot be phosphorylated (BS167) show abnormalities in growth and development. We sought to identify a bZIP protein in Dictyostelium whose production is controlled by the eIF2α regulatory system.Cells disrupted in the bzpR gene had similar developmental defects as BS167 cells, including small entities, stalk defects, and reduced spore viability. β-galactosidase production was used to examine translation from mRNA containing the bzpR 5' UTR. While protein production was readily apparent and regulated temporally and spatially in wild type cells, essentially no β-galactosidase was produced in developing BS167 cells even though the lacZ mRNA levels were the same as those in wild type cells. Also, no protein production was observed in strains lacking IfkA or IfkB eIF2α kinases. GFP fusions, with appropriate internal controls, were used to directly demonstrate that the bzpR 5' UTR, possessing 7 uORFs, suppressed translation by 12 fold. Suppression occurred even when all but one uORF was deleted, and translational suppression was removed when the ATG of the single uORF was mutated.The findings indicate that BzpR regulates aspects of the development program in Dictyostelium, serving as a downstream effector of eIF2α phosphorylation. Its production is temporally and spatially regulated by eIF2α phosphorylation by IfkA and IfkB and through the use of uORFs within the bzpR 5' UTR

Search for the Decays B^0 -> D^{(*)+} D^{(*)-}

Using the CLEO-II data set we have searched for the Cabibbo-suppressed decays B^0 -> D^{(*)+} D^{(*)-}. For the decay B^0 -> D^{*+} D^{*-}, we observe one candidate signal event, with an expected background of 0.022 +/- 0.011 events. This yield corresponds to a branching fraction of Br(B^0 -> D^{*+} D^{*-}) = (5.3^{+7.1}_{-3.7}(stat) +/- 1.0(syst)) x 10^{-4} and an upper limit of Br(B^0 -> D^{*+} D^{*-}) D^{*\pm} D^\mp and B^0 -> D^+ D^-, no significant excess of signal above the expected background level is seen, and we calculate the 90% CL upper limits on the branching fractions to be Br(B^0 -> D^{*\pm} D^\mp) D^+ D^-) < 1.2 x 10^{-3}.Comment: 12 page postscript file also available through http://w4.lns.cornell.edu/public/CLNS, submitted to Physical Review Letter