Mechanical behavior of bovine nasal cartilage under static and dynamic loading

Abnormal mechanical loading may trigger cartilage degeneration associated with osteoarthritis. Tissue response to load has been the subject of several in vitro studies. However, simple stimuli were often applied, not fully mimicking the complex in vivo conditions. Therefore, a rolling/plowing explant test system (RPETS) was developed to replicate the combined in vivo loading patterns. In this work we investigated the mechanical behavior of bovine nasal septum (BNS) cartilage, selected as tissue approximation for experiments with RPETS, under static and dynamic loading. Biphasic material properties were determined and compared with those of other cartilaginous tissues. Furthermore, dynamic loading in plowing modality was performed to determine dynamic response and experimental results were compared with analytical models and Finite Elements (FE) computations. Results showed that BNS cartilage can be modeled as a biphasic material with Young's modulus E=2.03±0.7 MPa, aggregate modulus H_A=2.35±0.7 MPa, Poisson's ratio ν=0.24±0.07, and constant hydraulic permeability k₀=3.0±1.3×10⁻¹⁵ m⁴ (N s)⁻¹. Furthermore, dynamic analysis showed that plowing induces macroscopic reactions in the tissue, proportionally to the applied loading force. The comparison among analytical, FE analysis and experimental results showed that predicted tangential forces and sample deformation lay in the range of variation of experimental results for one specific experimental condition. In conclusion, mechanical properties of BNS cartilage under both static and dynamic compression were assessed, showing that this tissue behave as a biphasic material and has a viscoelastic response to dynamic forces.     

Genetic Variants and Early Cigarette Smoking and Nicotine Dependence Phenotypes in Adolescents

Background

While the heritability of cigarette smoking and nicotine dependence (ND) is well-documented, the contribution of specific genetic variants to specific phenotypes has not been closely examined. The objectives of this study were to test the associations between 321 tagging single-nucleotide polymorphisms (SNPs) that capture common genetic variation in 24 genes, and early smoking and ND phenotypes in novice adolescent smokers, and to assess if genetic predictors differ across these phenotypes.

Methods

In a prospective study of 1294 adolescents aged 12–13 years recruited from ten Montreal-area secondary schools, 544 participants who had smoked at least once during the 7–8 year follow-up provided DNA. 321 single-nucleotide polymorphisms (SNPs) in 24 candidate genes were tested for an association with number of cigarettes smoked in the past 3 months, and with five ND phenotypes (a modified version of the Fagerstrom Tolerance Questionnaire, the ICD-10 and three clusters of ND symptoms representing withdrawal symptoms, use of nicotine for self-medication, and a general ND/craving symptom indicator).

Results

The pattern of SNP-gene associations differed across phenotypes. Sixteen SNPs in seven genes (ANKK1, CHRNA7, DDC, DRD2, COMT, OPRM1, SLC6A3 (also known as DAT1)) were associated with at least one phenotype with a p-value <0.01 using linear mixed models. After permutation and FDR adjustment, none of the associations remained statistically significant, although the p-values for the association between rs557748 in OPRM1 and the ND/craving and self-medication phenotypes were both 0.076.

Conclusions

Because the genetic predictors differ, specific cigarette smoking and ND phenotypes should be distinguished in genetic studies in adolescents. Fifteen of the 16 top-ranked SNPs identified in this study were from loci involved in dopaminergic pathways (ANKK1/DRD2, DDC, COMT, OPRM1, and SLC6A3).

Impact

Dopaminergic pathways may be salient during early smoking and the development of ND.     

Evolution of enzymatic activity in the enolase superfamily: functional studies of the promiscuous o-succinylbenzoate synthase from Amycolatopsis

o-Succinylbenzoate synthase (OSBS) from Amycolatopsis, a member of the enolase superfamily, catalyzes the Mn2+-dependent exergonic dehydration of 2-succinyl-6R-hydroxy-2,4-cyclohexadiene-1R-carboxylate (SHCHC) to 4-(2'-carboxylphenyl)-4-oxobutyrate (o-succinylbenzoate or OSB) in the menaquinone biosynthetic pathway. This enzyme first was identified as an N-acylamino acid racemase (NAAAR), with the optimal substrates being the enantiomers of N-acetyl methionine. This laboratory subsequently discovered that this protein is a much better catalyst of the OSBS reaction, with the value of k(cat)/K(M), for dehydration, 2.5 x 10(5) M(-1) s(-1), greatly exceeding that for 1,1-proton transfer using the enantiomers of N-acetylmethionine as substrate, 3.1 x 10(2) M(-1) s(-1) [Palmer, D. R., Garrett, J. B., Sharma, V., Meganathan, R., Babbitt, P. C., and Gerlt, J. A. (1999) Biochemistry 38, 4252-8]. The efficiency of the promiscuous NAAAR reaction is enhanced with alternate substrates whose structures mimic that of the SHCHC substrate for the OSBS reaction, for example, the value of k(cat)/K(M) for the enantiomers of N-succinyl phenylglycine, 2.0 x 10(5) M(-1) s(-1), is comparable to that for the OSBS reaction. The mechanisms of the NAAAR and OSBS reactions have been explored using mutants of Lys 163 and Lys 263 (K163A/R/S and K263A/R/S), the putative acid/base catalysts identified by sequence alignments with other OSBSs, including the structurally characterized OSBS from Escherichia coli. Although none of the mutants display detectable OSBS or NAAAR activities, K163R and K163S catalyze stereospecific exchange of the alpha-hydrogen of N-succinyl-(S)-phenylglycine with solvent hydrogen, and K263R and K263 catalyze the stereospecific exchange the alpha-hydrogen of N-succinyl-(R)-phenylglycine, consistent with formation of a Mn2+-stabilized enolate anion intermediate. The rates of the exchange reactions catalyzed by the wild-type enzyme exceed those for racemization. That this enzyme can catalyze two different reactions, each involving a stabilized enediolate anion intermediate, supports the hypothesis that evolution of function in the enolase superfamily proceeds by pathways involving functional promiscuity.     

Plasmodium falciparum: sequence diversity and antibody recognition of the Merozoite surface protein-2 (MSP-2) in Brazilian Amazonia

The merozoite surface protein-2 (MSP-2) of Plasmodium falciparum comprises repeats flanked by dimorphic domains defining the allelic families FC27 and IC1. Here, we examined sequence diversity at the msp-2 locus in Brazil and its impact on MSP-2 antibody recognition by local patients. Only 25 unique partial sequences of msp-2 were found in 61 isolates examined. The finding of identical msp-2 sequences in unrelated parasites, collected 6-13 years apart, suggests that no major directional selection is exerted by variant-specific immunity in this malaria-endemic area. To examine antibody cross-reactivity, recombinant polypeptides derived from locally prevalent and foreign MSP-2 variants were used in ELISA. Foreign IC1-type variants, such as 3D7 (currently tested for human vaccination), were less frequently recognized than FC27-type and local IC1-type variants. Antibodies discriminated between local and foreign IC1-type variants, but cross-recognized structurally different local IC1-type variants. The use of evolutionary models of MSP-2 is suggested to design vaccines that minimize differences between local parasites and vaccine antigens.     

Ciprofibrate therapy in patients with hypertriglyceridemia and low high density lipoprotein (HDL)-cholesterol: greater reduction of non-HDL cholesterol in subjects with excess body weight (The CIPROAMLAT study)

Background

Microalbuminuria and subsequent progression to proteinuria and nephropathy is associated with increased oxidative stress, increased inflammatory cytokines and increased cardiovascular (CVD) risk. The common functional IL-6 -174G>C gene variant is also associated with elevated levels of inflammatory cytokines and CVD risk.

Methods

The aim of this study was to examine the association between the IL-6 -174G>C gene variant with plasma total antioxidant status (TAOS) in 552 subjects with type 2 diabetes in relation to urinary protein excretion.

Results

In subjects free from CVD, there was a significant interaction between urinary protein excretion (normoalbuminuria/ microalbuminuria/proteinuria) and the -174C allele (compared to -174GG) in determining plasma TAOS (p value for interaction = 0.03). In the -174C allele carriers there was a significant association between plasma TAOS and urinary protein excretion: normalbuminuria v microalbuminuria v proteinuria: 44.30% ± 11.32 vs. 39.74% ± 14.83 vs. 37.93% ± 16.42, ANOVA p = 0.025. In those with CVD, no interaction or association was observed with the -174C allele (p = 0.246).

Conclusion

The IL-6 -174G>C gene variant is associated with differences in plasma oxidative stress in response to altered protein excretion in subjects with type 2 diabetes.     

Marked inhibition of retinal neovascularization in rats following soluble-flt-1 gene transfer

BACKGROUND: In mouse models of retinopathy of prematurity (ROP) inhibitors of vascular endothelial growth factor (VEGF) functions administered systemically completely block retinal neovascularization. In contrast, selective ocular VEGF depletion has achieved an approx. 50% inhibition of retinal neovascular growth. It is unclear whether a more complete inhibition of new blood vessel development can be obtained with an anti-VEGF therapy localized to the eye. Therefore, the objective of the present study was to determine the effect of local anti-VEGF therapy in a different animal model which closely mimics human ROP. METHODS: Rats were exposed to alternating cycles of high and low levels of oxygen for 14 days immediately after birth; thereafter, they were intravitreally injected with an adenoviral vector expressing a secreted form of the VEGF receptor flt-1 (Ad.sflt), which acts by sequestering VEGF. Contralateral eyes were injected with the control vector carrying the reporter gene expressing beta-galactosidase (Ad.betaGal). RESULTS: At the peak of retinal neovascular growth, i.e. post-natal day 21 (P21), we observed up to 97.5% decrease in retinal neovascularization in animals injected with Ad.sflt. At the end of observation (P28), no significant difference in retinal vessel number was detected in both oxygen-injured and normoxic Ad.sflt-treated retinas compared with untreated or Ad.betaGal-treated retinas. CONCLUSION: Adenoviral-mediated sflt-1 gene transfer induces a near-complete inhibition of ischemia-induced retinal neovascularization in rats without affecting pre-existing retinal vessels.     

Global change‐driven effects on dissolved organic matter composition: Implications for food webs of northern lakes

Northern ecosystems are experiencing some of the most dramatic impacts of global change on Earth. Rising temperatures, hydrological intensification, changes in atmospheric acid deposition and associated acidification recovery, and changes in vegetative cover are resulting in fundamental changes in terrestrial–aquatic biogeochemical linkages. The effects of global change are readily observed in alterations in the supply of dissolved organic matter (DOM)—the messenger between terrestrial and lake ecosystems—with potentially profound effects on the structure and function of lakes. Northern terrestrial ecosystems contain substantial stores of organic matter and filter or funnel DOM, affecting the timing and magnitude of DOM delivery to surface waters. This terrestrial DOM is processed in streams, rivers, and lakes, ultimately shifting its composition, stoichiometry, and bioavailability. Here, we explore the potential consequences of these global change‐driven effects for lake food webs at northern latitudes. Notably, we provide evidence that increased allochthonous DOM supply to lakes is overwhelming increased autochthonous DOM supply that potentially results from earlier ice‐out and a longer growing season. Furthermore, we assess the potential implications of this shift for the nutritional quality of autotrophs in terms of their stoichiometry, fatty acid composition, toxin production, and methylmercury concentration, and therefore, contaminant transfer through the food web. We conclude that global change in northern regions leads not only to reduced primary productivity but also to nutritionally poorer lake food webs, with discernible consequences for the trophic web to fish and humans.     

Phenotypic seedling responses of a metal-tolerant mutant line of sunflower growing on a Cu-contaminated soil series: potential uses for biomonitoring of Cu exposure and phytoremediation

Background and aims

The potential use of a metal-tolerant sunflower mutant line for both biomonitoring and phytoremediating a Cu-contaminated soil series was investigated.

Methods

The soil series (21–1,170 mg Cu kg^?1) was sampled in field plots at control and wood preservation sites. Sunflowers were cultivated 1 month in potted soils under controlled conditions.

Results

pH and dissolved organic matter influenced Cu concentration in the soil pore water. Leaf chlorophyll content and root growth decreased as Cu exposure rose. Their EC₁₀ values corresponded to 104 and 118 μg Cu L^?1 in the soil pore water, 138 and 155 mg Cu kg^?1 for total soil Cu, and 16–18 mg Cu kg^?1 DW shoot. Biomass of plant organs as well as leaf area, length and asymmetry were well correlated with Cu exposure, contrary to the maximum stem height and leaf water content.

Conclusions

Physiological parameters were more sensitive to soil Cu exposure than the morphological ones. Bioconcentration and translocation factors and distribution of mineral masses for Cu highlighted this mutant as a secondary Cu accumulator. Free Cu²⁺ concentration in soil pore water best predicted Cu phytoavailability. The usefulness of this sunflower mutant line for biomonitoring and Cu phytoextraction was discussed.     

Prefrontal Response and Frontostriatal Functional Connectivity to Monetary Reward in Abstinent Alcohol-Dependent Young Adults

Although altered function in neural reward circuitry is widely proposed in models of addiction, more recent conceptual views have emphasized the role of disrupted response in prefrontal regions. Changes in regions such as the orbitofrontal cortex, medial prefrontal cortex, and dorsolateral prefrontal cortex are postulated to contribute to the compulsivity, impulsivity, and altered executive function that are central to addiction. In addition, few studies have examined function in these regions during young adulthood, when exposure is less chronic than in typical samples of alcohol-dependent adults. To address these issues, we examined neural response and functional connectivity during monetary reward in 24 adults with alcohol dependence and 24 psychiatrically healthy adults. Adults with alcohol dependence exhibited less response to the receipt of monetary reward in a set of prefrontal regions including the medial prefrontal cortex, lateral orbitofrontal cortex, and dorsolateral prefrontal cortex. Adults with alcohol dependence also exhibited greater negative correlation between function in each of these regions and that in the nucleus accumbens. Within the alcohol-dependent group, those with family history of alcohol dependence exhibited lower mPFC response, and those with more frequent drinking exhibited greater negative functional connectivity between the mPFC and the nucleus accumbens. These findings indicate that alcohol dependence is associated with less engagement of prefrontal cortical regions, suggesting weak or disrupted regulation of ventral striatal response. This pattern of prefrontal response and frontostriatal connectivity has consequences for the behavior patterns typical of addiction. Furthermore, brain-behavior findings indicate that the potential mechanisms of disruption in frontostriatal circuitry in alcohol dependence include family liability to alcohol use problems and more frequent use of alcohol. In all, these findings build on the extant literature on reward-circuit function in addiction and suggest mechanisms for disrupted function in alcohol dependence.