Intronic gene conversion in the evolution of human X-linked color vision genes

Human red and green visual pigment genes are X-linked duplicate genes. To study their evolutionary history, introns 2 and 4 (1,987 and 1,552 bp, respectively) of human red and green pigment genes were sequenced. Surprisingly, we found that intron 4 sequences of these two genes are identical and that the intron 2 sequences differ by only 0.3%. The low divergences are unexpected because the duplication event producing the two genes is believed to have occurred before the separation of the human and Old World monkey (OWM) lineages. Indeed, the divergences in the two introns are significantly lower than both the synonymous divergence (3.2% +/- 1.1%) and the nonsynonymous divergence (2.0% +/- 0.5%) in the coding sequences (exons 1-6). A comparison of partial sequences of exons 4 and 5 of human and OWM red and green pigment genes supports the hypothesis that the gene duplication occurred before the human-OWM split. In conclusion, the high similarities in the two intron sequences might be due to very recent gene conversion, probably during evolution of the human lineage.      

Homozygosity for a splice junction mutation in exon 8 of the gene encoding lysosomal acid lipase in a Spanish kindred with cholesterol ester storage disease (CESD)

Deficiency of lysosomal acid lipase is expressed in two distinct recognizable phenotypes. Wolman disease represents the severe early onset form, whereas cholesterol ester storage disease is the more benign late onset type. Previous studies have indicated that compound heterozygosity consisting of a G A mutation at the 3 splice junction of exon 8 (E8SJM-allele) together with a null allele of the gene encoding lysosomal acid lipase leads to cholesterol ester storage disease. We have now observed homozygosity for the G A splice junction mutation in a non-related Spanish kindred with the same disease. As expected, the residual activity of lysosomal acid lipase is higher in this case, suggesting that the E8SJM-allele is associated with low residual acid lipase activity. However, the phenotype of the homozygous propositus is more severe compared with the previously described case, indicating that no direct relationship exists between the genotype or residual LAL activity and the precise cholesterol or triglyceride levels in a given patient. Nevertheless, our findings provide convincing evidence that homozygosity for the E8SJM-allele causes cholesterol ester storage disease to at least the same extent as compound heterozygosity consisting of this allele and a null allele.This study was performed in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki     

Continuously improving the practice of cardiology

Guidelines for the management of patients with cardiovascular disease are designed to assist cardiologists and other physicians in their practice. Surveys are conducted to assess whether guidelines are followed in practice. The results of surveys on acute coronary syndromes, coronary revascularisation, secondary prevention, valvular heart disease and heart failure are presented. Comparing surveys conducted between 1995 and 2002, a gradual improvement in use of secondary preventive therapy is observed. Nevertheless, important deviations from established guidelines are noted, with a significant variation among different hospitals in the Netherlands and in other European countries. Measures for further improvement of clinical practice include more rapid treatment of patients with evolving myocardial infarction, more frequent use of clopidogrel and glycoprotein IIb/IIIa receptor blockers in patients with acute coronary syndromes, more frequent use of β-blockers in patients with heart failure and more intense measures to encourage patients to stop smoking. Targets for the proportion of patients who might receive specific therapies are presented.     

Plasma fatty acids and [13C]linoleic acid metabolism in preterm infants fed a formula with medium-chain triglycerides

Most preterm infant formulas contain medium-chain triacylglycerols (MCT), but the effects of MCT on polyunsaturated fatty acid status and metabolism are controversial. Thus, we studied the effects of MCT on linoleic acid metabolism using stable isotopes. Enterally fed preterm infants were randomized to receive for 7 days 40% of fat as MCT (n = 10) or a formula without MCT (n = 9). At study day 5, infants received orally 2 mg/kg body weight of (13)C-labeled linoleic acid. Fatty acids in plasma lipid classes and (13)C enrichment of phospholipid fatty acids were measured and tracer oxidation was monitored. Compared with the control group, the MCT group showed lower breath (13)CO(2) and higher plasma triacylglycerol contents of octanoic acid, of decanoic acid, and of total long-chain polyunsaturated fatty acids (57.1 +/- 4.4 micro mol/l vs. 37.9 +/- 4.8 micro mol/l, P < 0.01). Concentrations of several polyunsaturated fatty acids in plasma phospholipids and non esterified fatty acids were higher in the MCT group. (13)C concentrations in phospholipid n-6 fatty acids indicated no difference in the relative conversion of linoleic to arachidonic acid. We conclude that oral MCT effectively reduce polyunsaturated fatty acid and long chain polyunsaturated fatty acid oxidation in preterm infants without compromising endogenous n-6 long chain polyunsaturated fatty acid synthesis.     

Expression of chemokine receptors in normal and inflamed human intestine, tonsil, and liver--an immunohistochemical analysis with new monoclonal antibodies from the 8th international workshop and conference on human leucocyte differentiation antigens

Chemokines are important mediators involved in the recruitment of leucocytes to lymphoid tissues and to sites of inflammation. To identify suitable monoclonal antibodies for immunohistochemistry, we tested a panel of new reagents provided by the cytokine/chemokine receptor section of the 8th HLDA workshop on cryostat sections of normal human gut, tonsil, and liver. In addition, inflamed intestinal tissues from individuals with Crohn's disease and ulcerative colitis were analysed. Our results reveal an upregulated expression of chemokine receptors like CCR6, CCR7, CCR9, CXCR1, and CXCR3 in inflamed gut. Enhanced expression of such molecules likely contributes to the maintenance of inflammation in chronic inflammatory bowel disease.     

A unique sequence motif in the 54-kDa subunit of the chloroplast signal recognition particle mediates binding to the 43-kDa subunit

Chloroplasts contain a novel type of signal recognition particle (cpSRP) that consists of two proteins, cpSRP54 and cpSRP43. cpSRP is involved in the post-translational targeting of the nuclear encoded light-harvesting chlorophyll-binding proteins (LHCPs) to the thylakoid membrane by forming a soluble cpSRP.LHCP transit complex in the stroma. Despite high sequence homology between chloroplast and cytosolic SRP54 proteins, the 54-kDa subunit of cpSRP is unique in its ability to bind cpSRP43. In this report, we identified a 10-amino acid long segment of cpSRP54 that forms the cpSRP43-binding site. This segment is located at position 530-539 close to the C terminus of cpSRP54. In addition, we demonstrate that arginine at position 537 is essential for binding cpSRP43 and that mutation of arginine 536 drastically reduced cpSRP43 binding. Mutations within the cpSRP43-binding site of cpSRP54 that reduced or completely abolished cpSRP complex formation also did inhibit transit complex formation and integration of LHCP into the thylakoid membrane, reflecting the importance of these residues for LHCP targeting. Alignment studies revealed that the cpSRP43-binding site is conserved in chloroplast SRP54 proteins and is not present in any SRP54 subunit of cytosolic SRPs.     

Apolipoprotein A4-1/2 polymorphism and response of serum lipids to dietary cholesterol in humans

The response of serum lipids to dietary changes is to some extent an innate characteristic. One candidate genetic factor that may affect the response of serum lipids to a change in cholesterol intake is variation in the apolipoprotein A4 gene, known as the APOA4-1/2 or apoA-IVGln360His polymorphism. However, previous studies showed inconsistent results. We therefore fed 10 men and 23 women with the APOA4-1/1 genotype and 4 men and 13 women with the APOA4-1/2 or -2/2 genotype (carriers of the APOA4-2 allele) two diets high in saturated fat, one containing cholesterol at 12.4 mg/MJ, 136.4 mg/day, and one containing cholesterol at 86.2 mg/MJ, 948.2 mg/day. Each diet was supplied for 29 days in crossover design. The mean response of serum low density lipoprotein cholesterol was 0.44 mmol/l (17 mg/dl) in both subjects with the APOA4-1/1 genotype and in subjects with the APOA4-2 allele [95% confidence interval of difference in response, -0.20 to 0.19 mmol/l (-8 to 7 mg/dl)]. The mean response of high density lipoprotein cholesterol was also similar, 0.10 mmol/l (4 mg/dl), in the two APOA-4 genotype groups [95% confidence interval of difference in response, -0.07 to 0.08 mmol/l (-3 to 3 mg/dl)]. Thus, the APOA4-1/2 polymorphism did not affect the response of serum lipids to a change in the intake of cholesterol in this group of healthy Dutch subjects who consumed a background diet high in saturated fat. Knowledge of the APOA4-1/2 polymorphism is probably not a generally applicable tool for the identification of subjects who respond to a change in cholesterol intake.     

Empirical Fuel Consumption and CO2 Emissions of Plug‐In Hybrid Electric Vehicles

Plug‐in hybrid electric vehicles (PHEVs) combine electric and conventional propulsion. Official fuel consumption values of PHEVs are based on standardized driving cycles, which show a growing discrepancy with real‐world fuel consumption. However, no comprehensive empirical results on PHEV fuel consumption are available, and the discrepancy between driving cycle and empirical fuel consumption has been conjectured to be large for PHEV. Here, we analyze real‐world fuel consumption data from 2,005 individual PHEVs of five PHEV models and observe large variations in individual fuel consumption with deviation from test‐cycle values in the range of 2% to 120% for PHEV model averages. Deviations are larger for short‐ranged PHEVs. Among others, range and vehicle power are influencing factors for PHEV model fuel consumption with average direct carbon dioxide (CO₂) emissions decreasing by 2% to 3% per additional kilometer (km) of electric range. Additional simulations show that PHEVs recharged from renewable electricity can noteworthily reduce well‐to‐wheel CO₂ emissions of passenger cars, but electric ranges should not exceed 200 to 300 km since battery production is CO₂‐intense. Our findings indicate that regulations should (1) be based on real‐world fuel consumption measurements for PHEV, (2) take into account charging behavior and annual mileages, and (3) incentivize long‐ranged PHEV.     

The CHC22 Clathrin-GLUT4 Transport Pathway Contributes to Skeletal Muscle Regeneration

Mobilization of the GLUT4 glucose transporter from intracellular storage vesicles provides a mechanism for insulin-responsive glucose import into skeletal muscle. In humans, clathrin isoform CHC22 participates in formation of the GLUT4 storage compartment in skeletal muscle and fat. CHC22 function is limited to retrograde endosomal sorting and is restricted in its tissue expression and species distribution compared to the conserved CHC17 isoform that mediates endocytosis and several other membrane traffic pathways. Previously, we noted that CHC22 was expressed at elevated levels in regenerating rat muscle. Here we investigate whether the GLUT4 pathway in which CHC22 participates could play a role in muscle regeneration in humans and we test this possibility using CHC22-transgenic mice, which do not normally express CHC22. We observed that GLUT4 expression is elevated in parallel with that of CHC22 in regenerating skeletal muscle fibers from patients with inflammatory and other myopathies. Regenerating human myofibers displayed concurrent increases in expression of VAMP2, another regulator of GLUT4 transport. Regenerating fibers from wild-type mouse skeletal muscle injected with cardiotoxin also showed increased levels of GLUT4 and VAMP2. We previously demonstrated that transgenic mice expressing CHC22 in their muscle over-sequester GLUT4 and VAMP2 and have defective GLUT4 trafficking leading to diabetic symptoms. In this study, we find that muscle regeneration rates in CHC22 mice were delayed compared to wild-type mice, and myoblasts isolated from these mice did not proliferate in response to glucose. Additionally, CHC22-expressing mouse muscle displayed a fiber type switch from oxidative to glycolytic, similar to that observed in type 2 diabetic patients. These observations implicate the pathway for GLUT4 transport in regeneration of both human and mouse skeletal muscle, and demonstrate a role for this pathway in maintenance of muscle fiber type. Extrapolating these findings, CHC22 and GLUT4 can be considered markers of muscle regeneration in humans.