Aging: Why Do Organisms Live Too Long?

SummaryFruit flies selected to reproduce on the fifth day of adult life for many generations remarkably keep on living for six weeks, showing no change in lifespan. A mutation-accumulation experiment suggests that the same genes confer high early-life fitness and long life

Evolution of ageing as a tangle of trade-offs:energy versus function

Despite tremendous progress in recent years, our understanding of the evolution of ageing is still incomplete. A dominant paradigm maintains that ageing evolves due to the competing energy demands of reproduction and somatic maintenance leading to slow accumulation of unrepaired cellular damage with age. However, the centrality of energy trade-offs in ageing has been increasingly challenged as studies in different organisms have uncoupled the trade-off between reproduction and longevity. An emerging theory is that ageing instead is caused by biological processes that are optimized for early-life function but become harmful when they continue to run-on unabated in late life. This idea builds on the realization that early-life regulation of gene expression can break down in late life because natural selection is too weak to optimize it. Empirical evidence increasingly supports the hypothesis that suboptimal gene expression in adulthood can result in physiological malfunction leading to organismal senescence. We argue that the current state of the art in the study of ageing contradicts the widely held view that energy trade-offs between growth, reproduction, and longevity are the universal underpinning of senescence. Future research should focus on understanding the relative contribution of energy and function trade-offs to the evolution and expression of ageing

Aspects of self-diffusion of solvent in polymer-low molecular weight substance system

On the assumption of the independent behaviour of the holes necessary for diffusion it is shown that in the polymer-low molecular weight substance system at T>Tg + (80-100) where Tg is the glass transition point of the system, the temperature dependence of the self-diffusion coefficient D of the solvent may be described by an equation of the Arrhenius type with the activation energy constant ED, which was also observed experimentally. It was established that fall in the self-diffusion coefficient with rise in the content of the polymer in the system is due to kinematic restrictions on the movement of small molecules. Rise in ED with fall in the content of the solvent is due, in the main, to increase in the energy of formation of the hole. © 1984

The probability of return to the initial position for a particle diffusing in porous media

A recent approximate calculation (by Mitra and coworkers) of the probability density of return to the initial position by time t for a particle diffusing in a porous medium is shown to be incorrect and to yield systematic errors whose magnitudes depend on the nature of the sample and on t. Another approach to approximate calculation of this characteristic is proposed, and the resultant errors are estimated. The value that is proposed for calculation is the probability of the return of the diffusing particle to the plane that is perpendicular to the pulse gradient of the magnetic field and passes through the point of the initial particle position. These characteristics are compared by the example of self-diffusion of a liquid in sandstones. © 1999 MAHK "Hayka/Interperiodica"

Silver-spoon upbringing improves early-life fitness but promotes reproductive ageing in a wild bird

Early-life conditions can have long-lasting effects and organisms that experience a poor start in life are often expected to age at a faster rate. Alternatively, individuals raised in high-quality environments can overinvest in early-reproduction resulting in rapid ageing. Here we use a long-term experimental manipulation of early-life conditions in a natural population of collared flycatchers (Ficedula albicollis), to show that females raised in a low-competition environment (artificially reduced broods) have higher early-life reproduction but lower late-life reproduction than females raised in high-competition environment (artificially increased broods). Reproductive success of high-competition females peaked in late-life, when low-competition females were already in steep reproductive decline and suffered from a higher mortality rate. Our results demonstrate that ‘silver-spoon’ natal conditions increase female early-life performance at the cost of faster reproductive ageing and increased late-life mortality. These findings demonstrate experimentally that natal environment shapes individual variation in reproductive and actuarial ageing in nature

Self diffusion of phthalic acid ester molecules

A study was made of self diffusion of molecules of several pure phthalates (dimethylphthalate, dibutylphthalate and dioctylphthalate) and their molecules added to PVC by a NMR pulse method. It was shown that the temperature relation of the coefficient of self diffusion of pure phthalates is satisfactorily described by the Einstein-Hill theory. Self diffusion of phthalates introduced in PVC is treated on the basis of the activation theory. Energies of cavity formation in diffusion of single phthalate molecules in a PVC matrix were calculated. The relation between the activation energy of self diffusion and plasticizer concentration was described. It was shown that the type of self diffusion of phthalates depends on the state of the polymer matrix. © 1978

Intergenerational transfer of ageing: Parental age and offspring lifespan

The extent to which the age of parents at reproduction can affect offspring lifespan and other fitness-related traits is important in our understanding of the selective forces shaping life history evolution. In this article, the widely reported negative effects of parental age on offspring lifespan (the ‘Lansing effect’) is examined. Outlined herein are the potential routes whereby a Lansing effect can occur, whether effects might accumulate across multiple generations, and how the Lansing effect should be viewed as part of a broader framework, considering how parental age affects offspring fitness. The robustness of the evidence for a Lansing effect produced so far, potential confounding variables, and how the underlying mechanisms might best be unravelled through carefully designed experimental studies are discussed

Determination of some parameters of a porous medium-liquid system by the pulsed field gradient NMR

A possibility was considered to estimate the parameter of a porous medium S/Vp, where S and Vp are the surface area and the volume of pores, respectively, as well as the power of nuclear magnetic energy sinks ρ of a porous medium-liquid system by the example of randomly packed glass spheres 53-63 μm in diameter and acetone, water, or decane as a liquid medium. Estimates were made by analyzing the time dependences of the effective self-diffusion coefficient D(t) and P(t), the probability of return of a molecule to its initial position by time t. It was shown that the short-time parts of D(t) dependence allow us to obtain parameters S/Vp and ρ, whereas those of P(t), only the S/Vp, parameter. The values of ρ, obtained from D(t), and from the time of relaxation of longitudinal nuclear magnetization, differ from each other by an order of magnitude. As expected, the value of S/Vp, obtained for a given porous medium, is independent of the nature of introduced liquid

NMR relaxation and the state of solvent molecules in solutions of polyvinylchloride and polystyrene in dibutylphthalate

An analysis was made of temperature concentration dependences of spin-spin relaxation time and the coefficient of self-diffusion of dibutylphthalate molecules in solutions containing 0-20 vol. % PVC and PS. It was established that, in contrast with the PS solution, PVC solutions contain a small proportion of dibutylphthalate molecules, which are more inhibited, compared with the remaining mass of solvent, and are exchanged with the latter. © 1983