Genetic structure among populations in the endemic Hawaiian Plantago lineage: insights from microsatellite variation

Endemic Hawaiian species in the genus Plantago show considerable morphological and ecological diversity. Despite their variation, a recent phylogenetic analysis based on DNA sequence data showed that the group is monophyletic and that sequence variation among species and morphotypes is low. This lack of sequence polymorphisms resulted in an inability to resolve species and population affinities within the most recently derived clade of this lineage. To assess species boundaries, population genetic structure and interpopulation connectivity among the morphologically and ecologically distinct populations within this clade, genetic variation was examined using eight microsatellite loci. Within‐population genetic diversity was found to be lowest in the Maunaiu, Hawai'i population of the endangered P. hawaiensis, and highest in the large P. pachyphylla population from 'Eke, West Maui. Isolation by distance across the range of populations was detected and indicated restricted dispersal. This result is likely to be attributable to few interisland dispersal events in the evolutionary history of this lineage. Genetic differentiation within islands tended to be higher among populations occurring in contrasting bog and woodland habitats, suggesting ecological barriers to gene flow and the potential role of ecological divergence in population diversification. Overall, these results are consistent with findings from phylogenetic analysis of the entire lineage. Our data bring new insights regarding patterns of dispersal and population genetic structure to this endemic and endangered group of island taxa. As island environments become increasingly fragmented, information of this type has important implications for the successful management of these fragile populations and habitats.     

ER-bound protein tyrosine phosphatase PTP1B interacts with Src at the plasma membrane/substrate interface

PTP1B is an endoplasmic reticulum (ER) anchored enzyme whose access to substrates is partly dependent on the ER distribution and dynamics. One of these substrates, the protein tyrosine kinase Src, has been found in the cytosol, endosomes, and plasma membrane. Here we analyzed where PTP1B and Src physically interact in intact cells, by bimolecular fluorescence complementation (BiFC) in combination with temporal and high resolution microscopy. We also determined the structural basis of this interaction. We found that BiFC signal is displayed as puncta scattered throughout the ER network, a feature that was enhanced when the substrate trapping mutant PTP1B-D181A was used. Time-lapse and co-localization analyses revealed that BiFC puncta did not correspond to vesicular carriers; instead they localized at the tip of dynamic ER tubules. BiFC puncta were retained in ventral membrane preparations after cell unroofing and were also detected within the evanescent field of total internal reflection fluorescent microscopy (TIRFM) associated to the ventral membranes of whole cells. Furthermore, BiFC puncta often colocalized with dark spots seen by surface reflection interference contrast (SRIC). Removal of Src myristoylation and polybasic motifs abolished BiFC. In addition, PTP1B active site and negative regulatory tyrosine 529 on Src were primary determinants of BiFC occurrence, although the SH3 binding motif on PTP1B also played a role. Our results suggest that ER-bound PTP1B dynamically interacts with the negative regulatory site at the C-terminus of Src at random puncta in the plasma membrane/substrate interface, likely leading to Src activation and recruitment to adhesion complexes. We postulate that this functional ER/plasma membrane crosstalk could apply to a wide array of protein partners, opening an exciting field of research.     

Heterogeneity of the Stearoyl-CoA desaturase-1 (SCD1) Gene and Metabolic Risk Factors in the EPIC-Potsdam Study

Background

Stearoyl-CoA desaturase-1 (SCD1) is an enzyme involved in lipid metabolism. In mice and humans its activity has been associated with traits of the metabolic syndrome, but also with the prevention of saturated fatty acids accumulation and subsequent inflammation, whereas for liver fat content inconsistent results have been reported. Thus, variants of the gene encoding SCD1 (SCD1) could potentially modify metabolic risk factors, but few human studies have addressed this question.

Methods

In a sample of 2157 middle-aged men and women randomly drawn from the Potsdam cohort of the European Prospective Investigation into Cancer and Nutrition, we investigated the impact of 7 SCD1 tagging-single nucleotide polymorphisms (rs1502593, rs522951, rs11190480, rs3071, rs3793767, rs10883463 and rs508384) and 5 inferred haplotypes with frequency >5% describing 90.9% of the genotype combinations in our population, on triglycerides, body mass index (BMI), waist circumference (WC), glycated haemoglobin (HbA1c), high-sensitivity C-reactive protein (hs-CRP), gamma-glutamyltransferase (GGT), alanine aminotransferase (ALT) and fetuin-A.

Results

No significant associations between any of the SNPs or haplotypes and BMI, WC, fetuin-A and hs-CRP were observed. Associations of rs10883463 with triglycerides, GGT and HbA1c as well as of rs11190480 with ALT activity, were weak and became non-significant after multiple-testing correction. Also associations of the haplotype harbouring the minor allele of rs1502593 with HbA1c levels, the haplotype harbouring the minor alleles of rs11190480 and rs508384 with activity of ALT, and the haplotype harbouring the minor alleles of rs522951, rs10883463 and rs508384 with triglyceride and HbA1C levels and GGT activities did not withstand multiple-testing correction.

Conclusion

These findings suggest that there are no associations between common variants of SCD1 or its inferred haplotypes and the investigated metabolic risk factors. However, given the results from animal models, heterogeneity of human SCD1 warrants further investigation, in particular with regard to rare variants.     

N-acetyl-L-cysteine improves renal medullary hypoperfusion in acute renal failure

This study evaluated the effects of N-acetyl-L-cysteine (NAC), a free radical scavenger, and N(omega)-nitro-L-arginine methyl ester (L-NAME), a nitric oxide (NO) synthesis inhibitor, on the changes in renal function, intrarenal blood flow distribution (laser-Doppler flowmetry), and plasma peroxynitrite levels during the acute renal failure (ARF) produced by inferior vena cava occlusion (IVCO; 45 min) in anesthetized rats. Renal blood flow fell on reperfusion (whole kidney by -45.7%; cortex -58.7%, outer medulla -62.8%, and papilla -47.7%); glomerular filtration rate (GRF) also decreased (-68.6%), whereas fractional sodium excretion (FE(Na%)) and peroxynitrite and NO/NO plasma levels increased (189.5, 46.5, and 390%, respectively) after ischemia. Pretreatment with L-NAME (10 microg. kg(-1). min(-1)) aggravated the fall in renal blood flow seen during reperfusion (-60%). Pretreatment with NAC (150 mg/kg bolus + 715 microg. kg(-1). min(-1) iv) partially prevented those changes in renal function (GFR only fell by -29.2%, and FE(Na%) increased 119.4%) and laser-Doppler blood flow, especially in the outer medulla, where blood flow recovered to near control levels during reperfusion. These beneficial effects seen in rats given NAC seem to be dependent on the presence of NO, because they were abolished in rats pretreated with L-NAME. Also, the antioxidant effects of NAC prevented the increase in plasma peroxynitrite after ischemia. In conclusion, NAC ameliorates the renal failure and the outer medullary vasoconstriction induced by ICVO, effects that seem to be dependent on the presence of NO and the scavenging of peroxynitrite.     

Ferrum metabolism after permanence at extreme altitude on Mount Everest

High altitude has always intrigued physiologists because of the remarkable ability of man to adapt to the hostile environment. Despite numerous studies examining the physiological alterations occurring during exercise after exposure to hypoxia and the adaptative effects of sustained residence at altitude, several issues remain unresolved. The aim of investigation of the Spanish Medical Research Expedition to Mount Everest in 1992 was an extensive study on the physiological adaptations to the hypobaric environment at extreme altitude. We are presenting advance results the gasometry, acid-base parameters and ferrum metabolism.     

Elevated adiponectin and sTNFRII serum levels can predict progression to hepatocellular carcinoma in patients with compensated HCV1 cirrhosis

Background and aims

An obesity-related altered adipose tissue secretion is suggested as a risk factor for hepatocellular carcinoma (HCC) in patients with hepatitis C virus (HCV) cirrhosis. However, no prospective study has yet examined the predictive value of circulating adipokines and immuno-inflammatory biomarkers regarding this risk.

Methods

This was a case-control study nested in a prospective French national cohort of HCV-infected patients with biopsy-proven compensated cirrhosis.We selected 56 HCV1-infected patients who subsequently developed HCC (cases), and 96 controls matched for age, gender and diabetes, not developing HCC after a similar period. Adipokines and immuno-inflammatory biomarkers were determined on baseline frozen serum samples. Their influence on the occurrence of HCC was assessed using a mixed logistic regression model under univariate analysis and a backward stepwise procedure under multivariate analysis.

Results

The patients were mostly male (62.5%) with active HCV replication (83%) and had been followed for a median duration of 6.3 years during which 44.4% achieved a sustained viral response. Higher adiponectinemia levels were found in cases than in controls (P = 0.01). Levels of the immuno-inflammatory markers were similar in both groups except sTNFRII >5,000 pg/mL (52% cases versus 24% controls; P = 0.001). No marker was associated with histological steatosis. Under multivariate analysis, baseline adiponectin and sTNFRII levels were independently associated with the occurrence of HCC,alongside previous excessive alcohol intake and HCV viral load.

Conclusions

High baseline circulating adiponectin and sTNFRII levels were associated with an increased risk of HCC in patients with HCV1 cirrhosis, independently of their HCV replication status.

     

Neurochemical studies in the hypoxic brain: substance P, met-enkephalin, GABA and angiotensin converting enzyme

Exposure of 28 day old rats to moderate hypoxia (10% oxygen) for three weeks led to significant increases of immunoreactive levels of substance P and met-enkephalin in the substantia nigra but not in the corpus striatum, globus pallidus of hypothalamus.A similar group of animals exposed to hypoxia for three weeks showed decreased angiotensin converting enzyme activity in the corpus striatum and substantia nigra and decreased GABA levels in the substantia nigra. However, fifteen days after recovery from hypoxia these changes were no longer apparent.Exposure to chronic, moderate hypoxia can affect levels of putative neurotransmitters in the brain, and based on the present findings the substantia nigra or the striato-nigral pathways appear to be particularly vulnerable.     

A rapid technique to predict malting quality in barley prior to harvest

Samples of grain from three spring barley cultivars of differing malting quality were collected at regular intervals during four weeks prior to harvest. The samples were dried, then assessed for relative grain hardness using the "Milling Energy" test. Ranking order of the cultivars for this character, which relates strongly to malting quality, was unaltered throughout. In a further experiment, it was demonstrated that selection for milling energy could be successfully practised on oven-dried grain collected six weeks after ear emergence.     

Striatal Protection in nNOS Knock-Out Mice After Quinolinic Acid-Induced Oxidative Damage

Under pathological conditions, nitric oxide can become a mediator of oxidative cellular damage, generating an unbalance between oxidant and antioxidant systems. The participation of neuronal nitric oxide synthase (nNOS) in the neurodegeneration mechanism has been reported; the activation of N-methyl-d-aspartate (NMDA) receptors by agonist quinolinic acid (QUIN) triggers an increase in nNOS function and promotes oxidative stress. The aim of the present work was to elucidate the participation of nNOS in QUIN-induced oxidative stress in knock-out mice (nNOS?/?). To do so, we microinjected saline solution or QUIN in the striatum of wild-type (nNOS +/+), heterozygote (nNOS+/?), and knock-out (nNOS?/?) mice, and measured circling behavior, GABA content levels, oxidative stress, and NOS expression and activity. We found that the absence of nNOS provides a protection against striatal oxidative damage induced by QUIN, resulting in decreased circling behavior, oxidative stress, and a partial protection reflected in GABA depletion. We have shown that nNOS-derived NO is involved in neurological damage induced by oxidative stress in a QUIN-excitotoxic model.