Protonmotive force and bacterial sensing

The role of the proton gradient and external pH in the motility and chemotaxis of Bacillus subtilis was investigated. Presence of a substantial proton gradient is not necessary for motility or chemotaxis, as long as the electrical potential is sufficient to maintain motility. Changes in the proton gradient do, however, lead to changes in swimming behavior, and these changes are mediated by two processes. One is sensitive to external pH and probably operates through a pH receptor. The second is sensitive to changes in the proton gradient. When the level of the protonmotive force is high enough to maintain motiligy, changes in the components of the protonmotive force are sensed by the bacteria and lead to behavioral changes, but changes in the protonmotive force are not necessary for chemotaxis.     

Epigenetic changes during aging and their reprogramming potential

The aging process results in significant epigenetic changes at all levels of chromatin and DNA organization. These include reduced global heterochromatin, nucleosome remodeling and loss, changes in histone marks, global DNA hypomethylation with CpG island hypermethylation, and the relocalization of chromatin modifying factors. Exactly how and why these changes occur is not fully understood, but evidence that these epigenetic changes affect longevity and may cause aging, is growing. Excitingly, new studies show that age-related epigenetic changes can be reversed with interventions such as cyclic expression of the Yamanaka reprogramming factors. This review presents a summary of epigenetic changes that occur in aging, highlights studies indicating that epigenetic changes may contribute to the aging process and outlines the current state of research into interventions to reprogram age-related epigenetic changes.     

More on the determinants of the fertility transition

The economic approach to fertility is an application of the economics theory of consumer behavior. It is assumed that consumers of children are utility-maximizers with stable preferences over time. Thus, changes in fertility are related to changes in household income and the "price" of children. One concern in this approach is that demographic changes are a product of changes in tastes rather than exogenous changes in economic factors such as the earning ability of women. In this paper, the effect of economic variables on the demand for children in the United States in 1950, 1960, 1970, and 1980 is examined. Support is provided for the hypothesis that the earning ability of women is an important determinant of fertility.     

Structural and functional plasticity of dendritic spines – root or result of behavior?

Dendritic spines are multifunctional integrative units of the nervous system and are highly diverse and dynamic in nature. Both internal and external stimuli influence dendritic spine density and morphology on the order of minutes. It is clear that the structural plasticity of dendritic spines is related to changes in synaptic efficacy, learning and memory and other cognitive processes. However, it is currently unclear whether structural changes in dendritic spines are primary instigators of changes in specific behaviors, a consequence of behavioral changes, or both. In this review, we first examine the basic structure and function of dendritic spines in the brain, as well as laboratory methods to characterize and quantify morphological changes in dendritic spines. We then discuss the existing literature on the temporal and functional relationship between changes in dendritic spines in specific brain regions and changes in specific behaviors mediated by those regions. Although technological advancements have allowed us to better understand the functional relevance of structural changes in dendritic spines that are influenced by environmental stimuli, the role of spine dynamics as an underlying driver or consequence of behavior still remains elusive. We conclude that while it is likely that structural changes in dendritic spines are both instigators and results of behavioral changes, improved research tools and methods are needed to experimentally and directly manipulate spine dynamics in order to more empirically delineate the relationship between spine structure and behavior.     

Are long‐term widespread avian body size changes related to food availability? A test using contemporaneous changes in carotenoid‐based color

Recent changes in global climate have been linked with changes in animal body size. While declines in body size are commonly explained as an adaptive thermoregulatory response to climate warming, many species do not decline in size, and alternative explanations for size change exist. One possibility is that temporal changes in animal body size are driven by changes in environmental productivity and food availability. This hypothesis is difficult to test due to the lack of suitable estimates that go back in time. Here, we use an alternative, indirect, approach and assess whether continent‐wide changes over the previous 100 years in body size in 15 species of Australian birds are associated with changes in their yellow carotenoid‐based plumage coloration. This type of coloration is strongly affected by food availability because birds cannot synthesize carotenoids and need to ingest them, and because color expression depends on general body condition. We found significant continent‐wide intraspecific temporal changes in body size (wing length) and yellow carotenoid‐based color (plumage reflectance) for half the species. Direction and magnitude of changes were highly variable among species. Meta‐analysis indicated that neither body size nor yellow plumage color showed a consistent temporal trend and that changes in color were not correlated with changes in size over the past 100 years. We conclude that our data provide no evidence that broad‐scale variation in food availability is a general explanation for continent‐wide changes in body size in this group of species. The interspecific variability in temporal changes in size as well as color suggests that it might be unlikely that a single factor drives these changes, and more detailed studies of museum specimens and long‐term field studies are required to disentangle the processes involved.     

Explorations in statistics: correlation

Learning about statistics is a lot like learning about science: the learning is more meaningful if you can actively explore. This sixth installment of Explorations in Statistics explores correlation, a familiar technique that estimates the magnitude of a straight-line relationship between two variables. Correlation is meaningful only when the two variables are true random variables: for example, if we restrict in some way the variability of one variable, then the magnitude of the correlation will decrease. Correlation cannot help us decide if changes in one variable result in changes in the second variable, if changes in the second variable result in changes in the first variable, or if changes in a third variable result in concurrent changes in the first two variables. Correlation can help provide us with evidence that study of the nature of the relationship between x and y may be warranted in an actual experiment in which one of them is controlled.     

Interrelated mechanisms in reward and learning

This brief review is focused on recent work in our laboratory, in which we assayed nicotine-induced neurotransmitter changes, comparing it to changes induced by other compounds and examined the receptor systems and their interactions that mediate the changes. The primary aim of our studies is to examine the role of neurotransmitter changes in reward and learning processes. We find that these processes are interlinked and interact in that reward-addiction mechanisms include processes of learning and learning-memory mechanisms include processes of reward. In spite being interlinked, the two processes have different functions and distinct properties and our long-term aim is to identify factors that control these processes and the differences among the processes. Here, we discuss reward processes, which we define as changes examined after administration of nicotine, cocaine or food, each of which induces changes in neurotransmitter levels and functions in cognitive areas as well as in reward areas. The changes are regionally heterogeneous and are drug or stimulus specific. They include changes in the transmitters assayed (catecholamines, amino acids, and acetylcholine) and also in their metabolites, hence, in addition to release, uptake and metabolism are involved. Many receptors modulate the response with direct and indirect effects. The involvement of many transmitters, receptors and their interactions and the stimulus specificity of the response indicated that each function, reward and learning represents the involvement of different pattern of changes with a different stimulus, therefore, many different learning and many different reward processes are active, which allow stimulus specific responses. The complex pattern of reward-induced changes in neurotransmitters is only a part of the multiple changes observed, but one which has a crucial and controlling function.     

Inhibitors of protein and RNA synthesis block structural changes that accompany long-term heterosynaptic plasticity in Aplysia.

Synaptic connections between the sensory and motor neurons of Aplysia in culture undergo long-term facilitation in response to serotonin (5-HT) and long-term depression in response to FMRFamide. These long-term functional changes are dependent on the synthesis of macromolecules during the period in which the transmitter is applied and are accompanied by structural changes. There is an increase and a decrease, respectively, in the number of sensory neuron varicosities in response to 5-HT and FMRFamide. To determine whether macromolecular synthesis is also required for the structural changes, we examined in parallel the effects of inhibitors of protein (anisomycin) or RNA (actinomycin D) synthesis on the structural and functional changes. We have found that anisomycin and actinomycin D block both the enduring alterations in varicosity number and the long-lasting changes in synaptic potential. These results indicate that macromolecular synthesis is required for expression of the long-lasting structural changes in the sensory cells and that this synthesis is correlated with the long-term functional modulation of sensorimotor synapses.     

Modeling implications of food resource aggregation on animal migration phenology

The distribution of poikilotherms is determined by the thermal structure of the marine environment that they are exposed to. Recent research has indicated that changes in migration phenology of beluga whales in the Arctic are triggered by changes in the thermal structure of the marine environment in their summering area. If sea temperatures reflect the spatial distribution of food resources, then changes in the thermal regime will affect how homogeneous or clumped food is distributed. We explore, by individual‐based modelling, the hypothesis that changes in migration phenology are not necessarily or exclusively triggered by changes in food abundance, but also by changes in the spatial aggregation of food. We found that the level of food aggregation can significantly affect the relationship between the timing of the start of migration to the winter grounds and the total prey capture of individuals. Our approach strongly indicates that changes in the spatial distribution of food resources should be considered for understanding and quantitatively predicting changes in the phenology of animal migration.     

Quantifying Post- Laser Ablation Prostate Therapy Changes on MRI via a Domain-Specific Biomechanical Model: Preliminary Findings

Focal laser ablation destroys cancerous cells via thermal destruction of tissue by a laser. Heat is absorbed, causing thermal necrosis of the target region. It combines the aggressive benefits of radiation treatment (destroying cancer cells) without the harmful side effects (due to its precise localization). MRI is typically used pre-treatment to determine the targeted area, and post-treatment to determine efficacy by detecting necrotic tissue, or tumor recurrence. However, no system exists to quantitatively evaluate the post-treatment effects on the morphology and structure via MRI. To quantify these changes, the pre- and post-treatment MR images must first be spatially aligned. The goal is to quantify (a) laser-induced shape-based changes, and (b) changes in MRI parameters post-treatment. The shape-based changes may be correlated with treatment efficacy, and the quantitative effects of laser treatment over time is currently poorly understood. This work attempts to model changes in gland morphology following laser treatment due to (1) patient alignment, (2) changes due to surrounding organs such as the bladder and rectum, and (3) changes due to the treatment itself. To isolate the treatment-induced shape-based changes, the changes from (1) and (2) are first modeled and removed using a finite element model (FEM). A FEM models the physical properties of tissue. The use of a physical biomechanical model is important since a stated goal of this work is to determine the physical shape-based changes to the prostate from the treatment, and therefore only physical real deformations are to be allowed. A second FEM is then used to isolate the physical, shape-based, treatment-induced changes. We applied and evaluated our model in capturing the laser induced changes to the prostate morphology on eight patients with 3.0 Tesla, T2-weighted MRI, acquired approximately six months following treatment. Our results suggest the laser treatment causes a decrease in prostate volume, which appears to manifest predominantly at the site of ablation. After spatially aligning the images, changes to MRI intensity values are clearly visible at the site of ablation. Our results suggest that our new methodology is able to capture and quantify the degree of laser-induced changes to the prostate. The quantitative measurements reflecting of the deformation changes can be used to track treatment response over time.     

More on the determinants of the fertility transition

Abstract

The economic approach to fertility is an application of the economics theory of consumer behavior. It is assumed that consumers of children are utility‐maximizers with stable preferences over time. Thus, changes in fertility are related to changes in household income and the “price” of children. One concern in this approach is that demographic changes are a product of changes in tastes rather than exogenous changes in economic factors such as the earning ability of women. In this paper, the effect of economic variables on the demand for children in the United States in 1950, 1960, 1970, and 1980 is examined. Support is provided for the hypothesis that the earning ability of women is an important determinant of fertility.     

Thermodynamic analyses of calcium binding to troponin C, calmodulin and parvalbumins by using microcalorimetry

Results of microcalorimetric titrations of calcium-binding proteins with calcium or magnesium have been reviewed and evaluated. Results were analyzed mostly in terms of heat capacity changes, which is most closely related to the structural changes of the molecule on metal binding. Two high-affinity sites of rabbit skeletal troponin C are distinguishable in terms of their affinity to calcium and associated enthalpy changes. Heat capacity changes on calcium binding to one of the two high-affinity sites is negative and is in the range ascribed to the ligand binding. In contrast, that to the other of the high-affinity sites is large and positive, indicating that a substantial area of hydrophobic groups become exposed to the solvent. In frog skeletal troponin C, the anomalous positive heat capacity changes occur in one of the low-affinity calcium-specific sites, so that this may be involved in the regulation of contraction. Unlike skeletal troponin C, both of the two high-affinity sites of cardiac troponin C show negative heat capacity changes. In calmodulin, heat capacity changes are positive but small, indicating that calcium binding may induce clustering of the hydrophobic residues on the surface of the molecule. In parvalbumins, heat capacity changes are negative, characteristic of most ligand binding.     

Whole-genome methylation analysis of aging human tissues identifies age-related changes in developmental and neurological pathways

Age-associated changes in the DNA methylation state can be used to assess the pace of aging. However, it is not understood what mechanisms drive these changes and whether these changes affect the development of aging phenotypes and the aging process in general. This study was aimed at gaining a more comprehensive understanding of aging-related methylation changes across the whole genome, and relating these changes to biological functions. It has been shown that skeletal muscle and blood monocytes undergo typical changes with aging. Using whole-genome bisulfite sequencing, we sought to characterize the genome-wide changes in methylation of DNA derived from both skeletal muscle and blood monocytes, and link these changes to specific genes and pathways through enrichment analysis. We found that methylation changes occur with aging at the locations enriched for developmental and neuronal pathways regulated in these two peripheral tissues. These results contribute to our understanding of changes in epigenome in human aging.     

Changes in the morphology of Ehrlich ascites tumour cells caused by hyperosmotic media

It was found that Ehrlich ascites tumour cells undergo significant morphology changes in media in which osmolarity is increased by NaCl or Hanks' balanced salt solution. The morphology changes include formation of filopodia- and lamellipodia-like cell surface protrusions. Their formation is enhanced by an addition of cytochalasin B. The data obtained suggest that both changes in plasma membrane properties and changes in activity of contractile apparatus participate in the formation of cell surface protrusions.     

Pain and motor control of the lumbopelvic region: effect and possible mechanisms.

Many authors report changes in the control of the trunk muscles in people with low back pain (LBP). Although there is considerable disagreement regarding the nature of these changes, we have consistently found differential effects on the deep intrinsic and superficial muscles of the lumbopelvic region. Two issues require consideration; first, the potential mechanisms for these changes in control, and secondly, the effect or outcome of changes in control for lumbopelvic function. Recent data indicate that experimentally induced pain may replicate some of the changes identified in people with LBP. While this does not exclude the possibility that changes in control of the trunk muscles may lead to pain, it does argue that, at least in some cases, pain may cause the changes in control. There are many possible mechanisms, including changes in excitability in the motor pathway, changes in the sensory system, and factors associated with the attention demanding, stressful and fearful aspects of pain. A new hypothesis is presented regarding the outcome from differential effects of pain on the elements of the motor system. Taken together these data argue for strategies of prevention and rehabilitation of LBP.     

Critical temperature and changes in cuticular lipids in the rabbit tick, Haemaphysalis leporispalustris

The epicuticle in the rabbit tick, Haemaphysalis leporispalustris, appeared to be continuously changing, with deposition and removal of lipids during and after engorgement. These changes were accompanied by corresponding changes in critical temperature. The correlation between changes in critical temperature and composition of cuticular lipids (i.e. changes in the number, types, and relative concentration of lipid classes) suggested that changes in lipid composition could be responsible for changes in critical temperature.A hypothesis, alternative to those of Beament and Locke, is proposed to explain the phenomenon of critical temperature. At critical temperature, certain lipids probably change phase from crystal to liquid crystal, with hydrocarbon chains in a highly mobile condition. The hypothesis is not based on the presence of a water-proofing monolayer, and is supported by transition phenomena known in many lipids.     

The Influence of Aging on Skin and Oral Mucosa1

Although the skin of the elderly shows many clinically obvious changes such as wrinking, dryness and patchy pigmentation it is difficult to determine to what extent extrinsic factors are responsible. On the other hand the mucosa lining the mouth which is exposed to a different environment has been claimed to show many similar clinical changes. The literature describing age-associated cellular changes is replete with conflicting reports. This is compounded by confusion of what constitutes “old”. There is no consensus on age-associated changes of fundamental attributes such as epithelial thickness, rates of tissue turnover or metabolic activity. Studies being carried out by the author suggest that there are few structural changes which occur in all surface epithelia with age but glycolytic activity is significantly increased. Ultrastructurally, significant quantities of fine fibrillar material have been observed to be associated with the basement membrane of oral epithelium, blood vessels and nerve bundles in the cheek. It is concluded that structural and functional changes that occur in skin and mucosa with age have not yet been defined adequately and further research is necessary in this area.     

Statistical analyses of developmental sequences: the craniofacial region in marsupial and placental mammals

Heterochrony is most often thought to involve changes in the rate of development or maturation (rate changes). However, heterochrony can also involve changes in the timing of specific developmental events relative to other events (sequence changes). Sequence changes have received much less attention than have changes in developmental rates, in part because few methods exist for comparing developmental sequences. Here, we present two methods to statistically evaluate developmental sequence changes. First, Kendall's coefficient of concordance (W) is used to quantify overall similarity of developmental sequences in two or more groups of organisms, and second, ANOVA is used to identify the individual events that differ most in their relative developmental timing. Computer simulation is used to control for the nonindependence of species. We examine the sequence of developmental events in the craniofacial region of marsupial and placental mammals. We conclude that the most important differences in development in the two clades relate to the relative sequence of development of the central nervous system and somatic elements of the craniofacial region. The rationale behind the methods and their limitations are discussed, and the results from this study are compared with a previous analysis.     

Can macaroni penguins keep up with climate- and fishing-induced changes in krill?

Macaroni penguins have evolved to cope with the highly variable conditions of the Southern Ocean. However, changes in prey supply and patchiness potentially associated with changes in climate and krill fishing activity may be occurring too rapidly for the penguins to adapt. We use a stochastic dynamic programming model to examine how changes in both the mean and patchiness of krill supply may affect the foraging decisions, and therefore breeding success, of female macaroni penguins at South Georgia. We predict that rapid changes in the mean supply of prey will have more of an effect on the condition of the female and chick than changes in prey patchiness, and that changes in foraging behavior compensate for changes in prey up to a threshold point, beyond which breeding success is likely impacted. In particular, we predict that the location of the threshold is affected by whether or not the penguins are adapted to the prey environment in which they are foraging, with the female and chick receiving on average 20% less of their daily energetic requirement if the female is not foraging optimally.     

Clinical aspects of normal pubertal development.

Puberty is associated with changes in nearly all organs and structures of the body. The present paper reviews the clinical aspects of these changes, i.e. the growth and development of the gonads and of secondary sexual characteristics, the pubertal growth spurt, the changes in body composition and the differential growth of certain viscera. The marked sexual dimorphism of some of these changes and of their timing is also discussed.