Simulation of reproductive risk and emergence of female reproductive cessation

Using a simple computer model for evolution, we show that in a sexual population subject only to age-increasing reproductive risk, a cessation of female reproduction emerges.Comment: 11 pages including 3 figure

Control of Estrus in Gilts and Primiparous Sows

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Motoneurone synchronization for intercostal and abdominal muscles: interneurone influences in two different species

The contribution of branched-axon monosynaptic inputs in the generation of short-term synchronization of motoneurones remains uncertain. Here, synchronization was measured for intercostal and abdominal motoneurones supplying the lower thorax and upper abdomen, mostly showing expiratory discharges. Synchronization in the anaesthetized cat, where the motoneurones receive a strong direct descending drive, is compared with that in anaesthetized or decerebrate rats, where the direct descending drive is much weaker. In the cat, some examples could be explained by branched-axon monosynaptic inputs, but many others could not, by virtue of peaks in cross-correlation histograms whose widths (relatively wide) and timing indicated common inputs with more complex linkages, e.g., disynaptic excitatory. In contrast, in the rat, correlations for pairs of internal intercostal nerves were dominated by very narrow peaks, indicative of branched-axon monosynaptic inputs. However, the presence of activity in both inspiration and expiration in many of the nerves allowed additional synchronization measurements between internal and external intercostal nerves. Time courses of synchronization for these often consisted of combinations of peaks and troughs, which have never been previously described for motoneurone synchronization and which we interpret as indicating combinations of inputs, excitation of one group of motoneurones being common with either excitation or inhibition of the other. Significant species differences in the circuits controlling the motoneurones are indicated, but in both cases, the roles of spinal interneurones are emphasised. The results demonstrate the potential of motoneurone synchronization for investigating inhibition and have important general implications for the interpretation of neural connectivity measurements by cross-correlation

Autism in Glasgow: cumulative incidence and the effects of referral age, deprivation and geographical location

Background: Referrals to the Greater Glasgow Community Autism Team (CAT) made before the child's sixth birthday were analysed to obtain an estimation of the proportion of children in Greater Glasgow with childhood autism and investigate whether there were any variations in diagnosis rates, or in age at referral and diagnosis, depending on deprivation or geographical location. Methods: An analysis was made of the database recording referrals to Greater Glasgow CAT, between 2004 and 2007 inclusive, of children referred by age 6 years, comprising 584 cases. Cumulative incidence was calculated for childhood autism. Ages at referral and diagnosis were also analysed. Results: For this subset of children, there were 246 diagnosed cases of childhood autism, a cumulative incidence from 2004 until 2007 of 11.1 per year per 10 000 children aged 0–6 years. Of children with an eventual diagnosis of autism by age 6, 72% were referred by the age of 4 years. Deprivation was found to have an association with referral and diagnostic rates, with higher rates seen in the most deprived. There was geographical variation in the cumulative incidence of autism. Conclusion: Given that the populations were not known to differ in any manner that would lead to a true variation, the geographical variation in the cumulative incidence of autism in children up to 6 years in Greater Glasgow observed in this study is likely to represent differences in the care pathway between areas. Such differences may also explain the observed association with deprivation. Reasons for the variation are being explored

Change and Aging Senescence as an adaptation

Understanding why we age is a long-lived open problem in evolutionary biology. Aging is prejudicial to the individual and evolutionary forces should prevent it, but many species show signs of senescence as individuals age. Here, I will propose a model for aging based on assumptions that are compatible with evolutionary theory: i) competition is between individuals; ii) there is some degree of locality, so quite often competition will between parents and their progeny; iii) optimal conditions are not stationary, mutation helps each species to keep competitive. When conditions change, a senescent species can drive immortal competitors to extinction. This counter-intuitive result arises from the pruning caused by the death of elder individuals. When there is change and mutation, each generation is slightly better adapted to the new conditions, but some older individuals survive by random chance. Senescence can eliminate those from the genetic pool. Even though individual selection forces always win over group selection ones, it is not exactly the individual that is selected, but its lineage. While senescence damages the individuals and has an evolutionary cost, it has a benefit of its own. It allows each lineage to adapt faster to changing conditions. We age because the world changes.Comment: 19 pages, 4 figure

A semiclassical trace formula for the canonical partition function of one dimensional systems

We present a semiclassical trace formula for the canonical partition function of arbitrary one-dimensional systems. The approximation is obtained via the stationary exponent method applied to the phase-space integration of the density operator in the coherent state representation. The formalism is valid in the low temperature limit, presenting accurate results in this regime. As illustrations we consider a quartic Hamiltonian that cannot be split into kinetic and potential parts, and a system with two local minima. Applications to spin systems are also presented.Comment: 22 pages, 4 figures new section with applications to spin system

Nonequilibrium Dynamics of Interfaces and Lines

The lectures examine several problems related to non-equilibrium fluctuations of interfaces and flux lines. The first two introduce the phenomenology of depinning, with particular emphasis on interfaces and contact lines. The role of the anisotropy of the medium in producing different universality classes is elucidated. The last two lectures focus on the dynamics of lines, where transverse fluctuations are also important. We shall demonstrate how various non-linearities appear in the dynamics of driven flux lines. The universality classes of depinning, and also dynamic roughening, are illustrated in the contexts of moving flux lines, advancing crack fronts, and drifting polymers.Comment: 36 pages, TeX, includes 10 eps figures. Lectures delivered at the The 4th CTP Workshop on Statistical Physics: ``Dynamics of Fluctuating Interfaces and Related Phenomena", Seoul National University, Kore

Searching for Stability as we Age: The PCA-Biplot Approach

Principal component analysis (PCA) has been successfully applied to gait data; however, interpretation of the components is challenging. An alternative is to use a graphical display called biplot that gives insights into relationships and trends of data sets. Our goal was to demonstrate the sensitivity of gait variables to aging in elderly women with PCA-biplot. One hundred fifty-one elderly females (71.6±5.0 yrs), 152 adults (44.7±5.4 yrs) and 150 young (21.7±4.1 yrs) participated in the study. Gait spatial and temporal parameters were collected using a computerized carpet. PCA-biplot, discriminant analysis and MANOVA were used in the analysis. PCA-biplot revealed that elderly females walked with lower velocity, shorter step length, reduced swing time, higher cadence, and increased double support time compared to the other two groups. The greatest distances between the groups were along the variable step length with the elderly group showing a decrease of 8.4 cm in relation to the younger group. The discriminant function confirmed the importance of principal component 2 for group separation. Because principal component 2 was heavily weighted by step length and swing time, it represents a measure of stability. As women age they seek a more stable gait by decreasing step length, swing time, and velocity. PCA-biplot highlighted the importance of the variable step length in distinguishing between women of different age groups. It is well-known that as we age we seek a more stable gait. The PCA-biplot emphasized that premise and gave further important insights into relationships and trends of this complex data set

Double cloprostenol administration during mid luteal phase of oestrous cycle does not modify the interoestrous interval in gilts

The present study was undertaken to test the effect of two vulva injections of D-cloprostenol on day 7, 9 and 10 of oestrous cycle on the duration of the interestrous interval in gilts. Following a pre-treatment oestrous cycle, 87 gilts were assigned to receive vulva injections of 75 μg D-cloprostenol at 08:00 and 14:00 h on day 7 (D7; n=30), day 9 (D9; n=29) or day 10 (D10; n=28) of their second observed oestrous cycle. Across the treatments, the duration of the oestrous cycle with D-cloprostenol treatment (19.1±0.1 d) was not different from that of the previous oestrous cycle (20.1±0.4 days). Plasma progesterone concentrations were evaluated 6 h before and 24 and 72 h after D-cloprostenol treatment in the D9 group. Compared to pretreatment levels (9.6±0.4 ng/mL), plasma progesterone concentrations were reduced (P<0.05) at 24 h (6.3±1.0 ng/mL) and 72 h after treatment but complete luteolysis did not occur. These data indicate that in gilts double vulva administration of D-cloprostenol is not able to induce a complete luteolisys and hence the duration of the oestrous cycle is not modified

Aging and Death in an Organism That Reproduces by Morphologically Symmetric Division

In macroscopic organisms, aging is often obvious; in single-celled organisms, where there is the greatest potential to identify the molecular mechanisms involved, identifying and quantifying aging is harder. The primary results in this area have come from organisms that share the traits of a visibly asymmetric division and an identifiable juvenile phase. As reproductive aging must require a differential distribution of aged and young components between parent and offspring, it has been postulated that organisms without these traits do not age, thus exhibiting functional immortality. Through automated time-lapse microscopy, we followed repeated cycles of reproduction by individual cells of the model organism Escherichia coli, which reproduces without a juvenile phase and with an apparently symmetric division. We show that the cell that inherits the old pole exhibits a diminished growth rate, decreased offspring production, and an increased incidence of death. We conclude that the two supposedly identical cells produced during cell division are functionally asymmetric; the old pole cell should be considered an aging parent repeatedly producing rejuvenated offspring. These results suggest that no life strategy is immune to the effects of aging, and therefore immortality may be either too costly or mechanistically impossible in natural organisms