Effects of Competitive Triathlon Training on Telomere Length.

Telomeres act as a mitotic clock and telomere-related senescence has been linked to age-related physiological decline. There is increasing evidence lifestyle factors can influence telomere length (TL). The purpose of this study was to determine the effect of competitive triathlon training on TL. Seven competitive male triathletes and seven recreationally active males participated in the study. Relative TL was measured using quantitative polymerase chain reaction. Physiological parameters key to athletic performance such as maximal oxygen intake, lactate threshold, and running economy were also measured. Triathletes had longer telomeres than the recreationally active (1.257 ± 0.028 vs. 1.002 ± 0.014; p < .0001). Positive association was found between TL and maximal oxygen intake, lactate threshold, and running economy (R2 = .677, .683, and .696, respectively). This study indicates that competitive triathlon training buffers against age-related telomere shortening, and there is a correlation between exercise behaviors, higher maximal oxygen intake, and TL.

Polypharmacy and sun exposure: Implications for mitochondrial DNA deletions in skin.

Most somatic cells contain many copies of mitochondrial DNA (mtDNA). Because of both the high copy number and the lack of repair mechanisms available to mtDNA, damage to it largely goes unrepaired, and can accumulate over time. Large scale deletions are a recognised type of damage sustained by mtDNA as a consequence of exposure to the ultraviolet light in sunlight. A group of patients were identified as having abnormally high levels of either a 4977 base pair deletion (mtDNA4977) or 3895 base pair deletion (mtDNA3895), in mtDNA from sun exposed skin or skin suspected to be a non-melanoma skin cancer, but not in their non-sun exposed skin biopsies. In three of the four cases, skin cancer was ruled out due to histological testing. Additional factors from these patients' medical histories were studied, and it was noted that they shared diagnoses for multiple pathologies common to an older population, and that they were being treated with the same or related pharmaceuticals, including some that had been known to cause dermal side effects. Investigation into the biochemistry underlying the symptoms, the effects of sun exposure and side effects of the prescribed pharmaceuticals revealed a possible synergistic relationship leading to the localised high levels of mtDNA deletions.

Mitochondrial DNA deletion percentage in sun exposed and non sun exposed skin.

The percentages of mitochondrial genomes carrying the mtDNA3895 and the mtDNA4977 (common) deletion were quantified in sun exposed and non sun exposed skin biopsies, for five cohorts of patients varying either in sun exposure profile, age or skin cancer status. Non-melanoma skin cancer diagnoses are rising in Ireland and worldwide [12] but most risk prediction is based on subjective visual estimations of sun exposure history. A quantitative objective test for pre-neoplastic markers may result in better adherence to sun protective behaviours. Mitochondrial DNA (mtDNA) is known to be subject to the loss of a significant proportion of specific sections of genetic code due to exposure to ultraviolet light in sunlight. Although one such deletion has been deemed more sensitive, another, called the mtDNA4977 or common deletion, has proved to be a more useful indicator of possible risk in this study. Quantitative molecular analysis was carried out to determine the percentage of genomes carrying the deletion using non sun exposed and sun exposed skin biopsies in cohorts of patients with high or low sun exposure profiles and two high exposure groups undergoing treatment for NMSC. Results indicate that mtDNA deletions correlate to sun exposure; in groups with high sun exposure habits a significant increase in deletion number in exposed over non sun exposed skin occurred. An increase in deletion percentage was also seen in older cohorts compared to the younger group. The mtDNA3895 deletion was detected in small amounts in exposed skin of many patients, the mtDNA4977 common deletion, although present to some extent in non sun exposed skin, is suggested to be the more reliable and easily detected marker. In all cohorts except the younger group with relatively lower sun exposure, the mtDNA4977 deletion was more frequent in sun exposed skin samples compared to non-sun exposed skin.

In vitro oxygen availability modulates the effect of artesunate on HeLa cells.

BACKGROUND/AIM: Hypoxia can affect chemotherapeutic drug efficacy in cancer patients, yet related in vitro assays in oxygen-rich environment remain the norm. Such levels are well beyond normoxic/hypoxic levels typically experienced by normal tissues/tumor masses. The present study evaluated how artesunate anti-tumor efficacy is modulated by oxygen availability in HeLa cells and its implications for future in vitro analyses. MATERIALS AND METHODS: Real-time cell analysis was employed to evaluate HeLa cell toxicity to artesunate at 21%, 4% or 1% oxygen. Cell count analysis was performed to validate real-time data. RESULTS: An increase in artesunate efficacy was observed when oxygen concentration was reduced from atmospheric levels down to in vivo-relevant levels. CONCLUSION: Artesunate is more potent than originally reported using standard oxygen conditions during in vitro studies. The inclusion of this long overlooked variable as standard in future in vitro analysis procedures is warranted.

Monotonic and fatigue behavior of five clinically relevant conventional and highly crosslinked UHMWPEs in the presence of stress concentrations.

Five formulations of clinically relevant UHMWPE (conventional, moderately crosslinked annealed and remelted, and highly crosslinked annealed and remelted) were investigated in a physiologically relevant environment. Their monotonic stress-strain behavior in the presence of notches of two different severities and at two different displacement rates was examined using a custom developed video based system. It was found that both an elevation of yield stress and a truncation of orientation hardening took place under monotonic loading and that these changes were found to be material and elastic stress concentration factor dependent. The fatigue behavior of these materials was examined using the same geometries via a stress-life approach with failure defined as fracture of the specimen in the 1000 to 100,000 cycle lifetime range. The results were modeled using the Basquin relationship (σ=AN(b), where σ=stress and N=lifetime, and A and b are experimentally derived constants) via maximum likelihood estimation methods to account for specimen runout (no failure at 250,000cycles). The conventional material was found to have a greater slope, b, and intercept, A, than the crosslinked materials as well as appearing to have less variance in its failure distributions.

Simulating the effects of climate change on the distribution of an invasive plant, using a high resolution, local scale, mechanistic approach: challenges and insights.

The growing economic and ecological damage associated with biological invasions, which will likely be exacerbated by climate change, necessitates improved projections of invasive spread. Generally, potential changes in species distribution are investigated using climate envelope models; however, the reliability of such models has been questioned and they are not suitable for use at local scales. At this scale, mechanistic models are more appropriate. This paper discusses some key requirements for mechanistic models and utilises a newly developed model (PSS[gt]) that incorporates the influence of habitat type and related features (e.g., roads and rivers), as well as demographic processes and propagule dispersal dynamics, to model climate induced changes in the distribution of an invasive plant (Gunnera tinctoria) at a local scale. A new methodology is introduced, dynamic baseline benchmarking, which distinguishes climate-induced alterations in species distributions from other potential drivers of change. Using this approach, it was concluded that climate change, based on IPCC and C4i projections, has the potential to increase the spread-rate and intensity of G. tinctoria invasions. Increases in the number of individuals were primarily due to intensification of invasion in areas already invaded or in areas projected to be invaded in the dynamic baseline scenario. Temperature had the largest influence on changes in plant distributions. Water availability also had a large influence and introduced the most uncertainty in the projections. Additionally, due to the difficulties of parameterising models such as this, the process has been streamlined by utilising methods for estimating unknown variables and selecting only essential parameters.

Mitophagy and mitochondrial morphology in human melanoma-derived cells post exposure to simulated sunlight.

PURPOSE: To assess changes in mitochondrial morphology and mitophagy induced by simulated sunlight irradiation (SSI) and how these changes are modulated by mitochondrial activity and energy source. MATERIALS AND METHODS: Human malignant amelanotic melanoma A375 cells were pre-treated with either a mitochondrial activity enhancer, uncoupler or were either melanin or glutamine supplemented/starved for 4 hours pre-exposure to sunlight. A Q-Sun Solar Simulator (Q-Lab, Homestead, FL, USA) was employed to expose cells to simulated sunlight. Confocal microscopy imaging of A375 cells co-loaded with mitochondria and lysosome-specific fluorescent dyes was used to identify these organelles and predict mitophagic events. RESULTS: SSI induces pronounced changes in mitochondrial dynamics and mitophagy in exposed skin cells compared to control and these effects were modified by both glutamine and melanin. CONCLUSIONS: Mitochondrial dynamics and rate of mitophagy in melanoma cells are sensitive to even short bursts of environmentally relevant SSI. Mitochondrial dynamics, and its modulation, may also play a role in mitophagy regulation, cell survival and proliferation post SSI.

Cell-density-dependent changes in mitochondrial membrane potential and reactive oxygen species production in human skin cells post sunlight exposure.

BACKGROUND: Solar ultraviolet radiation (UVR) is the principal etiological factor in skin carcinogenesis. In vivo and in vitro studies have demonstrated previously that oxidative DNA damage, mitochondrial mass and mitochondrial membrane potential (MMP) changes are associated with skin cell response to UVR stress. METHODS: Spontaneously immortalized human skin keratinocytes were irradiated with increasing sub-lethal doses of simulated sunlight irradiation (SSI) using a Q-Sun solar simulator. The effects of SSI on reactive oxygen species (ROS) formation, mitochondrial mass and MMP were then determined. RESULTS: SSI induced mitochondrial mass increase post low SSI (0.25-2.5 J/cm²), whereas higher SSI doses (5.0 and 7.5 J/cm²) decreased mitochondrial mass. Mitochondrial mass increased with time post 5.0 J/cm² irradiation and all changes in mass were independent of cell density status. Changes in ROS and MMP were cell density dependent. Additionally, an inverted dose-dependent decrease in ROS formation was observed 3 h post SSI with the lower SSI dose (0.25 J/cm²). CONCLUSIONS: Observations from the present study suggest that changes in the cell's microenvironment (modeled through varying cell density) influence changes in MMP and ROS detoxifying responses in sun-exposed skin cells.

Altered mitochondrial function and genome frequency post exposure to γ-radiation and bystander factors.

PURPOSE: To further evaluate irregular mitochondrial function and mitochondrial genome damage induced by direct γ-irradiation and bystander factors in human keratinocyte (HPV-G) epithelial cells and hamster ovarian fibroblast (CHO-K1) cells. This is as a follow-up to our recent reports of γ-irradiation-induced loss of mitochondrial function and mitochondrial DNA (mtDNA) damage. MATERIALS AND METHODS: Mitochondrial function was evaluated post direct radiation and irradiated cell conditioned medium (ICCM) by determining: Activity of the individual complexes of oxidative phosphorylation (OxPhos); mtDNA-encoded protein synthesis; and mitochondrial genome frequency and mtDNA damage. RESULTS: Mitochondria show a loss of OxPhos enzyme function as early as 4 h post treatment with recovery observed 12-96 h in some but not all complexes demonstrating a non-uniform sensitivity to γ-radiation. We also identified irregular mtDNA-directed protein synthesis. Long range Polymerase Chain Reaction (PCR) analysis identified mitochondrial genome damage and real-time PCR identified increases in mitochondrial genome frequency. CONCLUSIONS: The study reaffirms the sensitive nature of mitochondria to both low-level direct radiation exposure and radiation-induced bystander factor mediated damage. Furthermore, we report for the first time, the loss of function in the enzymes of OxPhos post exposure to bystander factors and identify altered mtDNA-directed protein synthesis post both direct radiation and bystander factors.

Notched fatigue behavior of PEEK.

Poly(ether-ether-ketone) (PEEK) has been used as a load bearing orthopaedic implant material with clinical success. All of the orthopaedic applications contain stress concentrations (notches) in their design; however, little work has been done to examine the fatigue behavior of PEEK in the presence of a notch. This work examines both stress-life (S-N) fatigue behavior and the fracture behavior of unfilled PEEK under tension-tension loading in circumferentially grooved round bar specimens with different elastic stress concentration factors. It was found that the majority of the loading was elastic in nature, and that there was only a small portion on the lifetime where there was a detectable change in structural behavior prior to gross fracture. Fractographic analysis via SEM further elucidated the potential fracture micromechanisms. Additional analysis was conducted to estimate the percent of the lifetime spent in crack initiation vs. propagation, and it was found that the specimens spent the majority of the time in the crack initiation phase.

Management of chronic lateral instability due to lateral collateral ligament deficiency after total knee arthroplasty: a case report.

INTRODUCTION: Lateral instability following total knee arthroplasty (TKA) is a rare condition with limited report of treatment options. The objective of this case presentation is to demonstrate the outcomes of different surgical procedures performed in a single patient with lateral collateral ligament (LCL) deficiency. CASE PRESENTATION: We present a case of chronic lateral instability due to LCL deficiency after primary TKA in a 47-year-old Caucasian woman with an obesity problem. Multiple treatment options have been performed in order to manage this problem, including the following: ligament reconstruction; combined ligament reconstruction and constrained implant; and rotating-hinge knee prosthesis that was the most recent surgery. All ligament reconstruction procedures failed within one year. The varus-valgus constrained prosthesis provided stability for six years. CONCLUSIONS: Ligament reconstruction alone cannot provide enough stability for the treatment of chronic lateral instability in patients with obesity problems and LCL deficiency. When the reconstruction fails, a salvage procedure with rotating-hinge knee is still available.

Gene expression and enzyme activity of mitochondrial proteins in irradiated rainbow trout (Oncorhynchus mykiss, Walbaum) tissues in vitro.

In recent years ethical, legislative and economic pressures have created a renewed interest in the development of alternatives to in vivo animal experiments. In vitro studies, particularly those using cell cultures, have been used increasingly as tools to assess the degree of toxicity associated with or present in particular environments. While cell cultures are useful to give relative toxicity values, genotypic and phenotypic integrity may be compromised in the continuous artificial environment they experience. In addition, cell cultures lack the complexity of functional organs and thus do not truly represent the effects that toxins exert on organ and organism functionality. In this study, ex vivo tissue cultures of rainbow trout gill, skin and spleen samples were analyzed for variation of expression in genes associated with oxidative phosphorylation after exposure to ionizing radiation. Significant radiation-induced changes in gene expression and enzyme activity associated with the mitochondrial oxidative phosphorylation process were identified. The tissues examined in this study demonstrated an exposure threshold at which radiation dose stimulates an alteration in the regulatory activity of mitochondrial-associated genes. Spleen tissues exposed to low levels of radiation (0.1 Gy) appeared most sensitive whereas skin tissues proved least sensitive, reacting only to higher doses (>1 Gy). We propose this investigative approach as an innovative alternative to in vivo studies because it identifies toxic exposure in vitro and could significantly reduce the number of live-animal toxicity tests required.

The control of oxidative phosphorylation in the adrenal gland (Y1) cell line.

We determined the proportion of oxygen consumption due to oxidative phosphorylation by mitochondria in an adrenal gland cell line (Y1 cells). In addition we determined the relative proportion of in situ mitochondrial oxygen consumption attributable to (i) proton leak and (ii) ATP turnover in these cells. This approach allowed use of top-down elasticity analysis to determine control of oxidative phosphorylation by mitochondrial (a) proton leak flux (b) substrate oxidation flux and (c) ATP turnover flux, as a function of changes in in situ mitochondrial membrane potential. Our data show that resting oxygen consumptions rates of Y1 cells to be 87 +/- 7 nmolO/min/10(7) cells of which 38 +/- 3% was not due to oxidative phosphorylation. We demonstrated that mitochondrial proton leak accounted for 7 +/- 3% of total cellular oxygen consumption or 12 +/- 6% of resting mitochondrial oxygen consumption, with ATP turnover accounting for 55 +/- 3% of total cellular oxygen consumption or 78 +/- 6% of mitochondrial oxygen consumption. Control of resting mitochondrial oxygen consumption in Y1 cells was shared by (a) substrate oxidation flux (37 +/- 8%), (b) proton leak flux (15 +/- 8%) and (c) ATP turnover (56 +/- 8%). Our data demonstrate, for the first time, that the majority of oxygen consumption by resting Y1 cells is due to oxidative phosphorylation.

Ultrafast exciton fine structure relaxation dynamics in lead chalcogenide nanocrystals.

The rates of fine structure relaxation in PbS, PbSe, and PbTe nanocrystals were measured on a femtosecond time scale as a function of temperature with no applied magnetic field by cross-polarized transient grating spectroscopy (CPTG) and circularly polarized pump-probe spectroscopy. The relaxation rates among exciton fine structure states follow trends with nanocrystal composition and size that are consistent with the expected influence of material dependent spin-orbit coupling, confinement enhanced electron-hole exchange interaction, and splitting between L valleys that are degenerate in the bulk. The size dependence of the fine structure relaxation rate is considerably different from what is observed for small CdSe nanocrystals, which appears to result from the unique material properties of the highly confined lead chalcogenide quantum dots. Modeling and qualitative considerations lead to conclusions about the fine structure of the lowest exciton absorption band, which has a potentially significant bearing on photophysical processes that make these materials attractive for practical purposes.

Expansion of the coordinator role in orthopaedic residency program management.

The Accreditation Council of Graduate Medical Education's (ACGME) Data Accreditation System indicates 124 of 152 orthopaedic surgery residency program directors have 5 or fewer years of tenure. The qualifications and responsibilities of the position based on the requirements of orthopaedic surgery residency programs, the institutions that support them, and the ACGME Outcome Project have evolved the role of the program coordinator from clerical to managerial. To fill the void of information on the coordinators' expanding roles and responsibilities, the 2006 Association of Residency Coordinators in Orthopaedic Surgery (ARCOS) Career survey was designed and distributed to 152 program coordinators in the United States. We had a 39.5% response rate for the survey, which indicated a high level of day-to-day managerial oversight of all aspects of the residency program; additional responsibilities for other department or division functions for fellows, rotating medical students, continuing medical education of the faculty; and miscellaneous business functions. Although there has been expansion of the role of the program coordinator, challenges exist in job congruence and position reclassification. We believe use of professional groups such as ARCOS and certification of program coordinators should be supported and encouraged.

Increased mitochondrial mass in cells with functionally compromised mitochondria after exposure to both direct gamma radiation and bystander factors.

The bystander effect describes radiation-like damage in unirradiated cells either in the vicinity of irradiated cells or exposed to medium from irradiated cells. This study aimed to further characterize the poorly understood mitochondrial response to both direct irradiation and bystander factor(s) in human keratinocytes (HPV-G) and Chinese hamster ovarian cells (CHO-K1). Oxygen consumption rates were determined during periods of state 4, state 3 and uncoupled respiration. Mitochondrial mass was determined using MitoTracker FM. CHO-K1 cells showed significantly reduced oxygen consumption rates 4 h after exposure to 5 Gy direct radiation and irradiated cell conditioned medium (ICCM) and an apparent recovery 12-24 h later. The apparent recovery was likely due to the substantial increase in mitochondrial mass observed in these cells as soon as 4 h after exposure. HPV-G cells, on the other hand, showed a sustained increase in oxygen consumption rates after ICCM exposure and a transient increase 4 h after exposure to 5 Gy direct radiation. A significant increase in mitochondrial mass per HPV-G cell was observed after exposure to both direct radiation and ICCM. These findings are indicative of a stress response to mitochondrial dysfunction that increases the number of mitochondria per cell.

Time-resolved photoconductivity of PbSe nanocrystal arrays.

We report the sub-picosecond photoconductivity dynamics of chemically treated PbSe nanocrystal arrays utilizing time-resolved terahertz spectroscopy (TRTS). TRTS allows both the degree of interdot electronic coupling and the carrier dynamics to be extracted simultaneously. The following capping ligands bonded to the quantum dot surface were studied: hydrazine, ethylenediamine, butlyamine, and aniline. In addition, the arrays were treated with NaOH. We find that the treatments affect both the degree of electronic coupling and the carrier dynamics.

The release of bystander factor(s) from tissue explant cultures of rainbow trout (Onchorhynchus mykiss) after exposure to gamma radiation.

The bystander response has been documented in cell lines and cell cultures derived from aquatic species over the past several years. However, little work has been undertaken to identify a similar bystander response in tissue explant cultures from fish. In this study, indirect effects of ionizing gamma radiation on tissue explant cultures of fish were investigated. Tissue explants in culture were exposed to 0.5 Gy and 5 Gy gamma radiation from a 60Co teletherapy unit. A bystander response in Epithelioma papulosum cyprini (EPC) cells exposed to gamma-irradiated tissue conditioned medium from rainbow trout explants was investigated, and the effects on cell survival were quantified by the clonogenic survival assay. Dichlorofluorescein and rhodamine 123 fluorescent dyes were used to identify alterations in reactive oxygen species (ROS) and mitochondrial membrane potential (MMP), respectively. Results indicate a different response for the three tissue types investigated. Clonogenic assay results vary from a decrease in cell survival (gill) to no effect (skin) to a stimulatory effect (spleen). Results from fluorescence assays of ROS and MMP show similarities to clonogenic assay results. This study identifies a useful model for further studies relating to the bystander effect in aquatic organisms in vivo and ex vivo.

PbTe colloidal nanocrystals: synthesis, characterization, and multiple exciton generation.

We report an alternative synthesis and the first optical characterization of colloidal PbTe nanocrystals (NCs). We have synthesized spherical PbTe NCs having a size distribution as low as 7%, ranging in diameter from 2.6 to 8.3 nm, with first exciton transitions tuned from 1009 to 2054 nm. The syntheses of colloidal cubic-like PbSe and PbTe NCs using a PbO "one-pot" approach are also reported. The photoluminescence quantum yield of PbTe spherical NCs was measured to be as high as 52 +/- 2%. We also report the first known observation of efficient multiple exciton generation (MEG) from single photons absorbed in PbTe NCs. Finally, we report calculated longitudinal and transverse Bohr radii for PbS, PbSe, and PbTe NCs to account for electronic band anisotropy. This is followed by a comparison of the differences in the electronic band structure and optical properties of these lead salts.

Mitochondrial DNA point mutations and a novel deletion induced by direct low-LET radiation and by medium from irradiated cells.

Radiation damage incurred by nuclear DNA is well documented and interest is increasing in the properties of 'bystander' factor(s) and their ability to induce radiation-like damage in cells never exposed to radiation. 'Bystander' and direct low-LET radiation effects on the mitochondria, and more particularly the mitochondrial genome are less well understood. In this study HPV-G cells (a human keratinocyte cell line derived from human neonatal foreskin transfected with the HPV-16 virus) were exposed to either gamma-radiation doses as low as 5 mGy and up to 5 Gy from a 60Co teletherapy unit, or to growth medium taken from similarly irradiated cells, i.e. irradiated cell conditioned medium (ICCM). Mutation and deletion analysis was performed on mitochondrial DNA (mtDNA) 4-96 h after exposure. Primers flanking the so-called mitochondrial 'common deletion' were employed to assess its possible induction. Single-strand conformation polymorphism (SSCP) analysis was conducted to identify induced point mutations. The relative mitochondrial number per cell was analysed by semi-quantitative PCR (sqPCR). Results indicate the induction of a relatively novel deletion in the mitochondrial genome as early as 12 h after direct exposure to doses as low as 0.5 Gy and 24 h after exposure to 0.5-Gy ICCM. SSCP analysis identified the induction of point mutations, in a non-consistent manner, in only the D-loop region of the mitochondrial genome and only in cells exposed to 5 Gy, and neither in cells exposed to lower doses of direct radiation nor in those exposed to ICCM. SqPCR also identified an increase in the number of mitochondria per cell after both exposure to low level gamma-radiation and ICCM, indicative of a possible mechanism to respond to mitochondrial stress by increasing the number of mitochondria per cell.