These "Guidelines for training in Cardiovascular Magnetic Resonance" were developed by the Certification Committee of the Society for Cardiovascular Magnetic Resonance (SCMR) and approved by the SCMR ...Board of Trustees.
Telomeres, tandem repeats of TTAGGG at the ends of chromosomes, are highly dynamic structures that shorten in response to a variety of factors, including organismal stress and tissue‐specific growth ...rates. Cell turnover rates are frequently linked to their functions, resource availability and telomere dynamics. Using male red‐sided garter snakes, Thamnophis sirtalis parietalis, as a model, we investigated the relationship between telomere length in sperm cells, blood cells telomere length and a growth proxy (age‐adjusted body length and mass). This relationship is interesting because snakes exhibit indeterminate growth and because these garter snakes have a dissociated reproductive cycle where spermatogenesis occurs months prior to the mating season. In this study, we determined sperm telomere length (STL) and male age using qPCR and skeletochronology, respectively. Sperm telomere length correlated positively with snout–vent length (SVL) and with age‐adjusted SVL as a proxy for growth rate (residuals of size against age regression, hereafter growth), but not with age. Although an individual’s STL is correlated with blood telomere length (BTL), sperm telomeres are 60% longer than blood telomeres. In previous work, we have shown that BTL is shorter in older males and unrelated to SVL or any growth rate proxies. We hypothesized that STL is related to growth and SVL because growth and sperm production both occur during summer when resources are most abundant and stress lowest. This study is the first to compare telomere dynamics between cell types in a snake and supports growing evidence that telomere dynamics may be highly tissue‐specific and driven by the life‐history strategy of an organism.
Telomeres are biomarkers of disease and aging with implications for life history strategies across taxa. We show that larger male garter snakes have longer sperm telomeres, which contrasts with our previous work which indicated that blood telomere length is shorter in older and therefore longer males. This study is the first to compare telomere dynamics between sperm and blood cells in a snake and supports growing evidence that telomere dynamics may be highly tissue‐specific and driven by the life history strategy of an organism.
Life-history strategies vary dramatically between the sexes, which may drive divergence in sex-specific senescence and mortality rates. Telomeres are tandem nucleotide repeats that protect the ends ...of chromosomes from erosion during cell division. Telomeres have been implicated in senescence and mortality because they tend to shorten with stress, growth and age. We investigated age-specific telomere length in female and male red-sided garter snakes, Thamnophis sirtalis parietalis. We hypothesized that age-specific telomere length would differ between males and females given their divergent reproductive strategies. Male garter snakes emerge from hibernation with high levels of corticosterone, which facilitates energy mobilization to fuel mate-searching, courtship and mating behaviours during a two to four week aphagous breeding period at the den site. Conversely, females remain at the dens for only about 4 days and seem to invest more energy in growth and cellular maintenance, as they usually reproduce biennially. As male investment in reproduction involves a yearly bout of physiologically stressful activities, while females prioritize self-maintenance, we predicted male snakes would experience more age-specific telomere loss than females. We investigated this prediction using skeletochronology to determine the ages of individuals and qPCR to determine telomere length in a cross-sectional study. For both sexes, telomere length was positively related to body condition. Telomere length decreased with age in male garter snakes, but remained stable in female snakes. There was no correlation between telomere length and growth in either sex, suggesting that our results are a consequence of divergent selection on life histories of males and females. Different selection on the sexes may be the physiological consequence of the sexual dimorphism and mating system dynamics displayed by this species.
Telomeres are DNA-protein caps at the ends of chromosomes that have been shown to be associated with male fertility may be heritable, reflect environmental influences and predict life span in some ...taxa. If heritable, paternal telomere length would be transmitted via sperm in the form of sperm telomere length (STL). We, therefore, investigated STL, sperm number and velocity in the Australian-painted dragon lizard, Ctenophorus pictus, an agamid lizard with distinct male colour morphs and related reproductive tactics. We measured telomere length in the sperm and blood as well as superoxide levels, as a measure for the potential for oxidative stress and ejaculate quality. We also noted a male’s head colour (red, orange, yellow or blue) and whether or not they had a yellow gular bib. Previous research has reported that yellow males outcompete red males in sperm competition; we found that yellow males had significantly shorter STL than red males. Males with bibs had greater STL than did males without bibs. Superoxide levels measured in the blood were negatively correlated with STL. Whole blood TL and body length were weakly but positively correlated with STL. Superoxide measurements were negatively correlated with progressive sperm motility and straight line sperm velocity across all males. The ejaculates of males with bibs had lower sperm counts and velocity than males without bibs. Our research adds to the growing research that indicates the importance of considering both somatic and gametic telomeres when assessing the interaction between telomere dynamics, life history and reproductive strategies.
The usage of telomere length (TL) in blood as a proxy for the TL of other tissues relies on the assumption that telomere dynamics across all tissues are similar. However, telomere attrition can be ...caused by reactive oxygen species (ROS) which may vary with metabolic rate, which itself varies across organs depending upon the life history strategy of an organism. Thus, we chose to measure the telomeres of various cell types in juvenile painted dragon lizards, Ctenophorus pictus, given their unusual life history strategy. Individuals typically only experience a single mating season. We measured the TL of male and female dragons using qPCR and observed that TL varied with tissue type and sex. Telomeres of blood cells were longer than those of liver, heart, brain, and spleen, and females had longer telomeres than males. Brain telomeres in males were approximately half the length of those in females. Telomeric attrition in the male brain may be due to the need for rapid learning of reproductive tactics (territory patrol and defense, mate‐finding). Significant correlations between the TL of tissue types suggest that blood TL may be a useful proxy for the TL of other tissues. Our comparison of organ‐specific telomere dynamics, the first in a reptile, suggests that the usage of blood TL as a proxy requires careful consideration of the life history strategy of the organism.
Blood, brain, heart, liver, and spleen telomeres are largely correlated in juvenile painted dragon lizards, Ctenophorus pictus. Females have longer telomeres than males across all tissues and brain telomeres that are twice as long.
Standardized swim-up trials are used in in vitro fertilization clinics to select particularly motile spermatozoa in order to increase the probability of a successful fertilization. Such trials ...demonstrate that sperm with longer telomeres have higher motility and lower levels of DNA damage. Regardless of whether sperm motility, and successful swim-up to fertilization sites, is a direct or correlational effect of telomere length or DNA damage, covariation between telomere length and sperm performance predicts a relationship between telomere length and probability of paternity in sperm competition, a prediction that for ethical reasons cannot be tested on humans. Here, we test this prediction in sand lizards (Lacerta agilis) using experimental data from twice-mated females in a laboratory population, and telomere length in blood from the participating lizards. Female identity influenced paternity (while the mechanism was not identified), while relatively longer male telomeres predicted higher probability of paternity. We discuss potential mechanisms underpinning this result.
Telomeres in human fibroblasts shorten progressively during in vitro culturing and trigger replicative senescence. Furthermore, shortened telomeres can be used as biomarkers of disease. These ...observations have led to the suggestion that telomere dynamics may also be associated with viability and selection for life history variation in non‐human taxa. Model systems to examine this suggestion would particularly benefit from the coexistence of multiple phenotypes within the same species with different life history trade‐offs, since those could be compared in terms of telomere characteristics. This scenario also provokes the classic question of why one morph does not have marginally higher fitness and replaces the others. One explanation is that different morphs have different reproductive tactics with equal relative fitness. In Australian painted dragons (Ctenophorus pictus), males differ in head color, the presence or absence of a gular bib, and reproductive expenditure. Red males out‐compete yellow males in dominance contests, while yellow males copulate quickly and have higher success in sperm competition than red males. Males with bibs better defend partners against rival matings, at the cost of loss of body condition. We show that yellow‐headed and bib‐less males have longer telomeres than red, blue and bibbed males, suggesting that telomere length is positively associated with higher investment into self‐maintenance and less reproductive expenditure.
We have studied a polymorphic lizard with different reproductive tactics and investments and test the hypothesis that morphs differ in telomere dynamics in relation to those morph tactics.
We used polysomnography, echocardiography and ventilatory measurements to study 50 patients suspected of having OSA to determine a link to RVH. Twenty-eight patients (56 percent) had OSA and 20 (71 ...percent) of those had isolated RVH. We evaluated patients with RVH and divided them into two groups, those with apnea and those without apnea. The patients with sleep apnea were younger, weighed more, had greater BSA and had lower average oxygen saturations during the sleep study period. We divided the group with apnea into those with RVH and those without it. Those patients with RVH had a higher AI, longer average apnea time, a greater duration of longest apnea and a lower average oxygen saturation for the period of the sleep study. In addition, those with RVH had a lower average oxygen saturation during each apneic episode with a p value equaling 0.09.
(Chest 1991; 100:347-50)
Established methods for characterizing proteins typically require physical or chemical modification steps or cannot be used to examine individual molecules in solution. Ionic current measurements ...through electrolyte-filled nanopores can characterize single native proteins in an aqueous environment, but currently offer only limited capabilities. Here we show that the zeptolitre sensing volume of bilayer-coated solid-state nanopores can be used to determine the approximate shape, volume, charge, rotational diffusion coefficient and dipole moment of individual proteins. To do this, we developed a theory for the quantitative understanding of modulations in ionic current that arise from the rotational dynamics of single proteins as they move through the electric field inside the nanopore. The approach allows us to measure the five parameters simultaneously, and we show that they can be used to identify, characterize and quantify proteins and protein complexes with potential implications for structural biology, proteomics, biomarker detection and routine protein analysis.
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