Controls on fracture openness and reactivation in Forsmark, Sweden

In crystalline bedrock, the open fraction of the fracture network constitutes the main pathways for fluids. Many observations point out that the state of stress influences the open fraction, likely indicating recent reactivation. But how this occurs is still unresolved. We analyse the conditions for fracture reactivation from fracture data collected in the uppermost 1 km of bedrock in Forsmark, Sweden. The open fraction is mainly correlated to the stress acting normally on the fracture but even away from critical failure, leading us to analyse the potential fluid pressure required for reactivation, [Formula: see text]. We observe that 100% of the fractures are open when [Formula: see text] is hydrostatic, and the ratio decreases exponentially to a plateau of ~ 17% when [Formula: see text] is lithostatic and above. Exceptions are the oldest fractures, having a low open fraction independent of [Formula: see text]. We suggest that these results reflect past pressure build-ups, potentially related to recent glaciations, and developing only if the preexisting open fraction is large enough.

Weak Social Networks in Late Life Predict Incident Alzheimer's Disease: The Kuakini Honolulu-Asia Aging Study

BACKGROUND

We assessed 10-year longitudinal associations between late-life social networks and incidence of all-cause dementia (ACD), Alzheimer's disease (AD), and vascular dementia (VaD) in Japanese-American men.

METHODS

We prospectively analyzed, from baseline (1991-1993) through 1999-2000, 2636 initially nondemented Kuakini Honolulu-Asia Aging Study participants who remained dementia-free during the first 3 years of follow-up. Global cognition was evaluated by the Cognitive Abilities Screening Instrument (CASI); depressive symptoms by the 11-item Center for Epidemiologic Studies Depression (CES-D) Scale; and social networks by the Lubben Social Network Scale (LSNS). Median split of LSNS scores defined weak/strong social network groups. A panel of neurologists and geriatricians diagnosed and classified dementia; AD and VaD diagnoses comprised cases in which AD or VaD, respectively, were considered the primary cause of dementia.

RESULTS

Median (range) baseline age was 77 (71-93) years. Participants with weak (LSNS score ≤29) versus strong (>29) social networks had higher age-adjusted incidence (in person-years) of ACD (12.6 vs. 8.7; p = .014) and AD (6.7 vs. 4.0; p = .007) but not VaD (2.4 vs. 1.4; p = .15). Kaplan-Meier curves showed a lower likelihood of survival free of ACD (log-rank p < .0001) and AD (p = .0006) for men with weak networks. In Cox proportional hazards models adjusting for age, education, APOE ɛ4, prevalent stroke, depressive symptoms, and CASI score (all at baseline), weak networks predicted increased incidence of ACD (hazard ratio [HR] = 1.52, p = .009) and AD (HR = 1.67, p = .014) but not VaD (p > .2).

CONCLUSION

Weak social networks may heighten the risk of dementia and AD, underscoring the need to promote social connectedness in older adults.

LATE-LIFE SOCIAL NETWORKS AND INCIDENT ALZHEIMER'S DISEASE: THE KUAKINI HONOLULU-ASIA AGING STUDY

We assessed longitudinal associations between social networks and incidence of all-cause dementia, Alzheimer’s disease (AD) and vascular dementia in Kuakini Honolulu-Asia Aging Study participants over a 10-year follow-up period. Median split of Lubben Social Network Scale (LSNS) scores defined weak/strong social networks among 2636 men who were dementia-free at baseline (median age 77 years) and during the first 3 years. Kaplan-Meier curves showed that those with strong networks at baseline were less likely to develop all-cause dementia (p<0.0001) and AD (p=0.0006); probability of dementia-free survival at 10 years for strong and weak social network groups was 93.8% and 89.0%, respectively. Cox regression models adjusting for age and other baseline factors revealed associations of weak networks with increased risk of all-cause dementia (HR=1.52, 95%CI=1.11-2.08, p=0.009) and AD (HR=1.67, 95%CI=1.11-2.51, p=0.014). As strong social networks may protect against incident dementia and AD, and are associated with other health benefits, prevention of social isolation of older adults should be considered a priority.

FOXO3-MEDIATED PROTECTION AGAINST VASCULAR DEMENTIA RISK IN A CASE-CONTROL STUDY OF ASIAN AMERICAN MEN

The longevity-associated allele of FOXO3 is associated with a significant reduction in cardiovascular disease (CVD) risk in older adults. We hypothesized that dementia, which shares several risk factors with CVD, might also be related to FOXO3 genotype, particularly vascular dementia (VaD). Therefore, we utilized the Kuakini Honolulu Heart Program/Honolulu Asia Aging Study dataset to assess the relation of FOXO3 genotype to dementia risk. Preliminary analyses suggested that VaD had the strongest relation to FOXO3 genotype. Therefore, we performed larger, more detailed study of FOXO3 genotype and VaD risk in a 9-year nest case-control study. Chi-Square test was used to assess the association of dementia with FOXO3 genotype in a sample of 1504 Japanese-American male study participants, aged 71-93 years, at the baseline exam. General Linear Model was utilized to compare VaD risk factors between VaD cases and controls. Multivariate Logistic Regression was used to assess the association of VaD with FOXO3 genotype adjusting for birth year, education, APOE4 and other vascular risk factors. We found a significant protective association for carriers of the principal FOXO3 longevity-associated allele (SNP rs2802292 G allele-carriers) against VaD risk (OR = 0.66, 95% CI = 0.44-0.98, p = 0.0388). The protective association retained significance when controlling for common risk factors for VaD in a multivariate model. These data indicate a potential neuroprotective role for the FOXO3 longevity-associated genotype against vascular dementia. This finding merits validation studies in other cohort studies.

Analysis of Cell and Molecular Phenotypes of a Highly Replicated Longevity-Associated FOXO3 Variant in Older Adults

Aging demographics in the US, and other industrialized nations, are resulting in rapidly increasing health care costs from age-related diseases. New therapeutic interventions to extend healthspan in older adults requires understanding connections between basic aging biology and human longevity factors. Using clinical samples from the Kuakini Honolulu Heart Program (HHP) and their Offspring, we are examining potential links between molecular and cellular mechanisms of aging and the longevity associated FOXO3 genotype (carriage of SNP rs2802292 “G” allele). Telomere dynamics in leucocytes (LTL) have shown strong correlation with multiple lifestyle and health factors. We previously demonstrated a significant protective relation between FOXO3 longevity genotype and LTL in a cross-sectional study. Now we are assessing a longitudinal relation, at three time points over 20+ years, in older men. We are also exploring stem cell frequency and differentiation capacity in neurological and peripheral blood samples to assess FOXO3 genotype and human cell dynamics.

THE LONGEVITY ASSOCIATED ALLELE OF FOXO3 PROTECTS AGAINST TELOMERE ATTRITION DURING AGING

Telomere attrition in proliferative tissues is a hallmark feature of human aging. To date, the genetic influence on the rate of telomere attrition is poorly understood. Previously we discovered a variant of the FOXO3 gene that is strongly associated with human longevity, an observation that has been now reproduced in over a dozen independent studies. In the present study, we sought to assess the effect of the longevity associated variant of FOXO3 (rs2802292 - G allele) on the rate of telomere attrition during aging. The results from a cohort of Okinawan-Japanese (N=121), ranging in age from 25 – 94 years, demonstrates carriers of 1 or 2 copies of the longevity-associated G allele of FOXO3 showed markedly reduced rates of telomere loss in peripheral blood leucocytes as compared to carriers of the more common FOXO3 variant (TT – common genotype, m= -33bp/year, P=0.008). Interestingly, telomere shortening was not observed as a function of age for G allele carriers (m= -2bp/year, P>0.1). In an independent study of women (N=6,565) from the Nurses’ Health Study cohort, ranging in age from 40 to 70 years, a similar observation was found. Notably, carriers of the TT or GT FOXO3 genotype showed a significant decline in telomere length with age (m= -15.5 bp/year, P0.1). These results mark the first validated longevity gene variant showing an association with negligible loss of telomere length with age in humans.

Cognitive impairment, brain ischemia and shorter telomeres are predictors of mortality in the Japanese elderly: A 13-year prospective community-based study

OBJECTIVE

To examine whether cognitive impairment, deep white matter hyperintensity (DWMH) on brain MRI, and shorter telomere length would be predictors of mortality in community-dwelling Japanese elderly.

METHODS

We followed 259 individuals (74% of all the residents at age 70) from age 70 to 83 years. The mean observation period was 133 ± 34 months. The key clinical characteristics examined included DWMH on brain MRI and cognitive function. Telomere length was also measured in 81 subjects. Both univariate and multivariate analyses were performed.

RESULTS

Of the 259 subjects, 69 subjects (30 men, 39 women; 26.6%) died during the follow-up period. Cognitive impairment, smoking habits, diabetes mellitus, and moderate to severe DWMH were significant predictors of total mortality in univariate analysis. However, only cognitive impairment and moderate to severe DWMH remained as significant independent predictors of death in multivariate analysis. The rate of mortality increased with additional number of risk factors (cognitive impairment and DWMH). The total mortality of subjects with both cognitive impairment and DWMH was 71.4%. The median telomere length was 7.8 kb in the deceased and 8.2 kb in the living subjects. The deceased subjects had significantly shorter telomere length (P = .0025) than the living subjects. Telomere length with moderate to severe DWMH was higher than without moderate to severe DWMH on brain MRI (P = .017).

CONCLUSIONS

The present study revealed that cognitive impairment, DWMH, and shorter telomere length were significant predictors of total mortality in the community-dwelling Japanese elderly. Furthermore, the combination of cognitive impairment and DWMH increased the mortality rate, as compared with a single risk factor. It is also clarified that a significant difference was present in telomere length by severity of DWMH.

Effective Targeted Gene Knockdown in Mammalian Cells Using the piggyBac Transposase-based Delivery System

Nonviral gene delivery systems are rapidly becoming a desirable and applicable method to overexpress genes in various types of cells. We have recently developed a piggyBac transposase-based, helper-independent and self-inactivating delivery system (pmGENIE-3) capable of high-efficiency transfection of mammalian cells including human cells. In the following study, we have assessed the potential of this delivery system to drive the expression of short hairpin RNAs to knock down genes in human cells. Two independent pmGENIE-3 vectors were developed to specifically target knockdown of an endogenous gene, telomerase reverse transcriptase (TERT), in telomerase-positive human immortalized cell lines. As compared with a transposase-deficient vector, pmGENIE-3 showed significantly improved short-term transfection efficiency (~4-fold enhancement, 48 hours posttransfection) and long-term integration efficiency (~5-fold enhancement) following antibiotic selection. We detected a significant reduction of both TERT expression and telomerase activity in both HEK293 and MCF-7 breast carcinoma cells transfected with two pmGENIE-3 construct targeting distinct regions of TERT. Importantly, this knockdown of expression was sufficient to abrogate telomerase function since telomeres were significantly shortened (3-4 Kb, P < 0.001) in both TERT-targeted cell lines following antibiotic selection of stable integrants. Together, these data show the capacity of the piggyBac nonviral delivery system to stably knockdown gene expression in mammalian cells and indicate the potential to develop novel tumor-targeting therapies.Molecular Therapy-Nucleic Acids (2013) 2, e137; doi:10.1038/mtna.2013.61; published online 3 December 2013.

A novel telomerase activator suppresses lung damage in a murine model of idiopathic pulmonary fibrosis

The emergence of diseases associated with telomere dysfunction, including AIDS, aplastic anemia and pulmonary fibrosis, has bolstered interest in telomerase activators. We report identification of a new small molecule activator, GRN510, with activity ex vivo and in vivo. Using a novel mouse model, we tested the potential of GRN510 to limit fibrosis induced by bleomycin in mTERT heterozygous mice. Treatment with GRN510 at 10 mg/kg/day activated telomerase 2–4 fold both in hematopoietic progenitors ex vivo and in bone marrow and lung tissue in vivo, respectively. Telomerase activation was countered by co-treatment with Imetelstat (GRN163L), a potent telomerase inhibitor. In this model of bleomycin-induced fibrosis, treatment with GRN510 suppressed the development of fibrosis and accumulation of senescent cells in the lung via a mechanism dependent upon telomerase activation. Treatment of small airway epithelial cells (SAEC) or lung fibroblasts ex vivo with GRN510 revealed telomerase activating and replicative lifespan promoting effects only in the SAEC, suggesting that the mechanism accounting for the protective effects of GRN510 against induced lung fibrosis involves specific types of lung cells. Together, these results support the use of small molecule activators of telomerase in therapies to treat idiopathic pulmonary fibrosis.

Horizontal pre-asymptotic solute transport in a plane fracture with significant density contrasts

We investigate the dispersion of a finite amount of solute after it has been injected into the laminar flow occurring in a horizontal smooth fracture of constant aperture. When solute buoyancy is negligible, the dispersion process eventually leads to the well-known asymptotic Taylor-Aris dispersion regime, in which the solute progresses along the fracture at the average fluid velocity, according to a one-dimensional longitudinal advection-dispersion process. This paper addresses more realistic configurations for which the solute-induced density contrasts within the fluid play an important role on solute transport, in particular at small and moderate times. Flow and transport are coupled, since the solute distribution impacts the variations in time of the advecting velocity field. Transport is simulated using (i) a mathematical description based on the Boussinesq approximation and (ii) a numerical scheme based on a finite element analysis. This enables complete characterization of the process, in particular at moderate times for which existing analytical models are not valid. At very short times as well as very long times, the overall downward advective solute mass flow is observed to scale as the square of the injected concentration. The asymptotic Taylor-Aris effective dispersion coefficient is reached eventually, but vertical density currents, which are significant at short and moderate times, are responsible for a systematic retardation of the asymptotic mean solute position with respect to the frame moving at the mean fluid velocity, as well as for a time shift in the establishment of the asymptotic dispersion regime. These delays are characterized as functions of the Péclet number and another non-dimensional number which we call advective Archimedes number, and which quantifies the ratio of buoyancy to viscous forces. Depending on the Péclet number, the asymptotic dispersion is measured to be either larger or smaller than what it would be in the absence of buoyancy effects. Breakthrough curves measured at distances larger than the typical distance needed to reach the asymptotic dispersion regime are impacted accordingly. These findings suggest that, under certain conditions, density/buoyancy effects may have to be taken into consideration when interpreting field measurement of solute transport in fractured media. They also allow an estimate of the conditions under which density effects related to fracture wall roughness are likely to be significant.

A modified Lagrangian-volumes method to simulate nonlinearly and kinetically sorbing solute transport in heterogeneous porous media

Transport in subsurface environments is conditioned by physical and chemical processes in interaction, with advection and dispersion being the most common physical processes and sorption the most common chemical reaction. Existing numerical approaches become time-consuming in highly-heterogeneous porous media. In this paper, we discuss a new efficient Lagrangian method for advection-dominated transport conditions. Modified from the active-walker approach, this method comprises dividing the aqueous phase into elementary volumes moving with the flow and interacting with the solid phase. Avoiding numerical diffusion, the method remains efficient whatever the velocity field by adapting the elementary volume transit times to the local velocity so that mesh cells are crossed in a single numerical time step. The method is flexible since a decoupling of the physical and chemical processes at the elementary volume scale, i.e. at the lowest scale considered, is achieved. We implement and validate the approach to the specific case of the nonlinear Freundlich kinetic sorption. The method is relevant as long as the kinetic sorption-induced spreading remains much larger than the dispersion-induced spreading. The variability of the surface-to-volume ratio, a key parameter in sorption reactions, is explicitly accounted for by deforming the shape of the elementary volumes.

Hypoxia: are stem cells in it for the long run?

Adult stem cells must persist throughout life to ensure continuous replenishment of dead or damaged cells in various tissues of the body. While numerous studies have already begun to identify some of the factors and mechanisms that regulate long term function and survival of stem cells, there is still much to learn in this regard. A growing body of evidence suggests that various types of stem cells exist in a hypoxic microenvironment, which may be conducive to stem cell longevity. We have recently shown that the oxygen dependent transcription factor hypoxia inducible factor 1alpha (Hif1α) is essential for maintenance of functional levels of telomerase in murine embryonic stem cells (mES). Importantly, long-term proliferation of mES cells with reduced Hif1α levels led to telomere shortening and ultimately cell senescence. Studies by others over the past 10 years has also indicated that hypoxia and Hif expression are essential for self-renewal and are involved in the regulation of proliferation for some types of stem cells. We now report our view regarding the effects and mechanisms by which hypoxia may regulate the long-term maintenance of stem cell populations.

RNAi screen for telomerase reverse transcriptase transcriptional regulators identifies HIF1alpha as critical for telomerase function in murine embryonic stem cells

In various types of stem cells, including embryonic stem (ES) cells and hematopoietic stem cells, telomerase functions to ensure long-term self-renewal capacity via maintenance of telomere reserve. Expression of the catalytic component of telomerase, telomerase reverse transcriptase (Tert), which is essential for telomerase activity, is limiting in many types of cells and therefore plays an important role in establishing telomerase activity levels. However, the mechanisms regulating expression of Tert in cells, including stem cells, are presently poorly understood. In the present study, we sought to identify genes involved in the regulation of Tert expression in stem cells by performing a screen in murine ES (mES) cells using a shRNA expression library targeting murine transcriptional regulators. Of 18 candidate transcriptional regulators of Tert expression identified in this screen, only one candidate, hypoxia inducible factor 1 alpha (Hif1alpha), did not have a significant effect on mES cell morphology, survival, or growth rate. Direct shRNA-mediated knockdown of Hif1alpha expression confirmed that suppression of Hif1alpha levels was accompanied by a reduction in both Tert mRNA and telomerase activity levels. Furthermore, gradual telomere attrition was observed during extensive proliferation of Hif1alpha-targeted mES cells. Switching Hif1alpha-targeted mES cells to a hypoxic environment largely restored Hif1alpha levels, as well as Tert expression, telomerase activity levels, and telomere length. Together, these findings suggest a direct effect of Hif1alpha on telomerase regulation in mES cells, and imply that Hif1alpha may have a physiologically relevant role in maintenance of functional levels of telomerase in stem cells.

Attenuated expression of SECIS binding protein 2 causes loss of telomeric reserve without affecting telomerase

The family of selenoproteins have a broad range of functions, including protection against oxidative damage. Previous studies have shown that elevated levels of oxidative damage can induce accelerated loss of telomeric DNA during proliferation of mammalian cells. The incorporation of selenocysteine (Sec) into proteins in mammalian cells requires the Sec insertion sequence (SECIS) binding protein 2 (SBP2). Thus in the present study we have assessed the effect of knocking down the expression of SBP2 on telomere length. Following knock-down of SBP2 expression in two different human cell lines, the MSTO mesothelioma cell line ( approximately 5Kb average telomere length) and SY5Y neuroblastoma cell line (approximately 4.2Kb average telomere length), we observed a significant reduction (-0.6 to -1.1 Kb; P <or= 0.01) in telomere length as compared to control cells. This reduction in telomere length was independent of affects on telomerase, since both telomerase activity levels and Tert mRNA expression levels were not altered by knock-down of SBP2 expression. Furthermore, telomeres were particularly sensitive to S1 nuclease digestion following SBP2 knock-down, indicating an increased frequency of oxidative damage-induced lesions in the telomeric DNA in these cells. Together, these observations imply that selenoproteins may help protect telomeric reserve in mammalian cells.

Fetal growth restriction is associated with accelerated telomere shortening and increased expression of cell senescence markers in the placenta

A hallmark of fetal growth restriction (FGR) is restricted placental development and insufficient nutrient supply to the fetus. It has previously been shown that activity levels of telomerase, the enzyme responsible for completing replication of telomeric DNA during cell division, is suppressed in FGR placenta samples as compared to control placenta samples from donors of the same gestational age. Here we examine whether telomere length maintenance is also compromised in FGR placenta samples. Southern analysis of telomere length for placenta and cord blood samples from 32 FGR and 36 control donors, ranging in gestational age from 37 to 40 weeks, revealed significantly shorter telomeres (P<or=0.001) in FGR placenta samples, but not cord blood samples. Furthermore, analysis of telomerase extracts, RNA and DNA placental samples from donors with and without idiopathic FGR confirmed a direct association between suppression of telomerase activity and reduced telomere length in FGR placenta. In addition, expression levels of markers of telomere-induced senescence, p21, p16 and EF-1 alpha, were significantly elevated in FGR placenta samples (P<or=0.01). These observations support a direct affect of reduced telomerase activity levels on the placental pathology associated with FGR.

Flow in multiscale fractal fracture networks

The paper aims at defining the flow models, including equivalent permeability, that are appropriate for multiscale fracture networks. As a prerequisite of the flow analysis, we define the scaling nature of fracture networks that is likely quantified by power-law length distributions whose exponent fixes the contribution of large fractures versus small ones. Despite the absence of any characteristic length scale of the power-law model, the flow structure appears to contain three length scales at the very maximum: the connecting scale, the channelling scale, and the homogenization scale, above which the equivalent permeability tends to a constant value. These scales, including their existence, depend on the fracture length distribution and on the transmissivity distribution per fracture. They are basic in defining the flow properties of fracture networks.

Advective transport in the percolation backbone in two dimensions

We show that, in the case of advective transport on the percolation backbone, the relevant structure below the correlation length is an ensemble of tortuous paths, rather than the classical links-nodes-blobs system. These paths are embedded in the few largest blobs that dominate the structure of the backbone. We find numerically that the mean particle displacement differs from the prediction given by classical finite-size scaling arguments. We also show that because of the complex velocity distribution between the paths, the mean first-passage time of the particles cannot be inferred directly from the mean particle displacement.

Percolation parameter and percolation-threshold estimates for three-dimensional random ellipses with widely scattered distributions of eccentricity and size

In fractured materials of very low matrix permeability, fracture connectivity is the first-order determinant of the occurrence of flow. For systems having a narrow distribution of object sizes (short-range percolation), a first-order percolation criterion is given by the total excluded volume which is almost constant at threshold. In the case of fractured media, recent observations have demonstrated that the fracture-length distribution is extremely large. Because of this widely scattered fracture-length distribution, the classical expression of the total excluded volume is no longer scale invariant at the percolation threshold and has no finite limit for infinitely large systems. Thus, the classical estimation method of the percolation threshold established in short-range percolation becomes useless for the connectivity determination of fractured media. In this study, we derive an expression for the total excluded volume that remains scale invariant at the percolation threshold and that can thus be used as the proper control parameter, called the parameter of percolation in percolation theory. We show that the scale-invariant expression of the total excluded volume is the geometrical union normalized by the system volume rather than the summation of the mutual excluded volumes normalized by the system volume. The summation of the mutual excluded volume (classical expression) remains linked to the number of intersections between fractures, whereas the normalized geometrical union of the mutual excluded volume (our expression) can be essentially identified with the percolation parameter. Moreover, fluctuations of this percolation parameter at threshold with length and eccentricity distributions remain limited within a range of less than one order of magnitude, giving in turn a rough percolation criterion. We finally show that the scale dependence of the percolation parameter causes the connectivity of fractured media to increase with scale, meaning especially that the hydraulic properties of fractured media can dramatically change with scale.

Estimation of the saturation of serum transferrin by an electrophoretic technique

An electrophoretic method is described for estimating the saturation of serum transferrin. After first precipitating most of the other proteins with Rivanol, the apo-, mono-, and di-ferric transferrins are separated by electrophoresis in urea-polyacrylamide gel. Densitometric scanning enables the percentage saturation to be calculated.