Physiology Commons^™

Scfkmd Controls Cytokinin Signaling By Regulating The Degradation Of Type-B Response Regulators, Hyo Jung Kim, Yi-Hsuan Chiang, Joseph J. Kieber, G. Eric Schaller

Dartmouth Scholarship

Cytokinins are plant hormones that play critical roles in growth and development. In Arabidopsis, the transcriptional response to cytokinin is regulated by action of type-B Arabidopsis response regulators (ARRs). Although central elements in the cytokinin signal transduction pathway have been identified, mechanisms controlling output remain to be elucidated. Here we demonstrate that a family of F-box proteins, called the kiss me deadly (KMD) family, targets type-B ARR proteins for degradation. KMD proteins form an S-phase kinase-associated PROTEIN1 (SKP1)/Cullin/F-box protein (SCF) E3 ubiquitin ligase complex and directly interact with type-B ARR proteins. Loss-of-function KMD mutants stabilize type-B ARRs and exhibit an …

Molecular Remodeling Of Tip Links Underlies Mechanosensory Regeneration In Auditory Hair Cells, Artur A. Indzhykulian, Ruben Stepanyan, Anastasiia Nelina, Kateri J. Spinelli, Zubair M. Ahmed, Inna A. Belyantseva, Thomas B. Friedman, Peter G. Barr-Gillespie, Gregory I. Frolenkov

Physiology Faculty Publications

Sound detection by inner ear hair cells requires tip links that interconnect mechanosensory stereocilia and convey force to yet unidentified transduction channels. Current models postulate a static composition of the tip link, with protocadherin 15 (PCDH15) at the lower and cadherin 23 (CDH23) at the upper end of the link. In terminally differentiated mammalian auditory hair cells, tip links are subjected to sound-induced forces throughout an organism's life. Although hair cells can regenerate disrupted tip links and restore hearing, the molecular details of this process are unknown. We developed a novel implementation of backscatter electron scanning microscopy to visualize simultaneously …

Does Naloxone Reinstate Secondary Hyperalgesia In Humans After Resolution Of A Burn Injury? A Placebo-Controlled, Double-Blind, Randomized, Cross-Over Study, Manuel P. Pereira, Mads U. Werner, Thomas K. Ringsted, Michael C. Rowbotham, Bradley K. Taylor, Joergen B. Dahl

Physiology Faculty Publications

INTRODUCTION: Development of secondary hyperalgesia following a cutaneous injury is a centrally mediated, robust phenomenon. The pathophysiological role of endogenous opioid signalling to the development of hyperalgesia is unclear. Recent animal studies, carried out after the resolution of inflammatory pain, have demonstrated reinstatement of tactile hypersensitivity following administration of μ-opioid-receptor-antagonists. In the present study in humans, we analyzed the effect of naloxone when given after the resolution of secondary hyperalgesia following a first-degree burn injury.

METHODS: Twenty-two healthy volunteers were included in this placebo-controlled, randomized, double-blind, cross-over study. Following baseline assessment of thermal and mechanical thresholds, a first-degree burn injury …

From Gibbons To Gymnasts: A Look At The Biomechanics And Neurophysiology Of Brachiation In Gibbons And Its Human Rediscovery, Emma Et Pennock

Student Works

This conference paper serves to examine the evolutionary linkages of a brachiating ancestor in humans, the biomechanical and neurophysiology of modern day brachiators, and the human rediscovery of this form of locomotion. Brachiation is arguably one of the most metabolically effective modes of travel by any organism and can be observed most meritoriously in Gibbons. The purpose of the research conducted for this paper was to encourage further exploration of the neurophysiological similarities and differences between humans and non-human primates. The hope is that in spurring more interest and research in this area, further possibilities for rehabilitating brain injury will …

Summary Of Papers Presented At The 2012 Seventh International Cough Symposium, Peter V. Dicpinigaitis, Giovanni A. Fontana, Lu-Yuan Lee, Milos Tatar

Physiology Faculty Publications

Twenty six papers were presented as posters in the Seventh International Symposium on Cough; 12 papers were presented in the Basic Science of Cough session, and 14 papers presented in the Clinical Science of Cough session. These papers explored a wide spectrum of cough-related areas including pathophysiological mechanisms, treatment and detection of cough, and symptom assessment and perception, and were grouped into several general themes for facilitate the discussion. Studies presented in these posters have provided new information that should improve our knowledge on the basic physiology and pharmacology of cough, and the peripheral and central neural mechanisms involved in …

A Comparative Genomics Approach To Using High-Throughput Gene Expression Data To Study Limb Regeneration In Ambystoma Mexicanum And Danio Rerio: Developing A More Completely Annotated Database, Justin Bolinger

Honors College

Axolotl (Ambystoma mexicanum) and the zebrafish (Danio rerio) represent organisms extensively studied because of their remarkable capability of fully regenerating completely functional tissues after a traumatic event takes place. However, the research conducted with regards to the genomics of these two organisms has remained fairly independent of each other. The intent of this study is to bridge this gap and connect genes between axolotl and the zebrafish by use a “Rosetta stone” framework to develop a database comparing gene expression data obtained from both microarraybased experiments and high-throughput DNA sequencing of axolotl and zebrafish mRNA and miRNA. Using gene data …

Direct Reprogramming Of Mouse Embryonic Fibroblasts Into Gabaergic Neurons, Nicholas J. Wasko

Honors Scholar Theses

Recent studies in which mouse and human fibroblasts were directly reprogrammed into functional neurons have demonstrated that lineage-specific transcription factors can override differentiation processes previously thought to be irreversible. Notably, three factors have been shown to be required for the induction of neural cell fate. Subsequent experiments have identified additional factors capable of generating specific neuronal subtypes, including motor neurons and dopaminergic neurons, but the factors necessary for inducing GABAergic neuronal fate have yet to be elucidated. Here, factors linked to GABAergic fate were transfected into mouse fibroblasts in order to identify candidate factors for inhibitory interneuron direct reprogramming. Results …

Nuclear Localization Of Cpi-17, A Protein Phosphatase-1 Inhibitor Protein, Affects Histone H3 Phosphorylation And Corresponds To Proliferation Of Cancer And Smooth Muscle Cells., Masumi Eto, Jason A Kirkbride, Rishika Chugh, Nana Kofi Karikari, Jee In Kim

Department of Molecular Physiology and Biophysics Faculty Papers

CPI-17 (C-kinase-activated protein phosphatase-1 (PP1) inhibitor, 17kDa) is a cytoplasmic protein predominantly expressed in mature smooth muscle (SM) that regulates the myosin-associated PP1 holoenzyme (MLCP). Here, we show CPI-17 expression in proliferating cells, such as pancreatic cancer and hyperplastic SM cells. Immunofluorescence showed that CPI-17 was concentrated in nuclei of human pancreatic cancer (Panc1) cells. Nuclear accumulation of CPI-17 was also detected in the proliferating vascular SM cell culture and cells at neointima of rat vascular injury model. The N-terminal 21-residue tail domain of CPI-17 was necessary for the nuclear localization. Phospho-mimetic Asp-substitution of CPI-17 at Ser12 attenuated the nuclear …

Divergent Protein Motifs Direct Ef-P Mediated Translational Regulation In Salmonella And Escherichia Coli, Steven J. Hersch, Mengchi Wang, S. Betty Zou, Kyung-Mee Moon, Leonard J. Foster, Michael Ibba, William Wiley Navarre

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

Elongation factor P (EF-P) is a universally conserved bacterial translation factor homologous to eukaryotic/archaeal initiation factor 5A. In Salmonella, deletion of the efp gene results in pleiotropic phenotypes, including increased susceptibility to numerous cellular stressors. Only a limited number of proteins are affected by the loss of EF-P, and it has recently been determined that EF-P plays a critical role in rescuing ribosomes stalled at PPP and PPG peptide sequences. Here we present an unbiased in vivo investigation of the specific targets of EF-P by employing stable isotope labeling of amino acids in cell culture (SILAC) to compare the …

Intrinsic Apoptotic Pathway: Effects Of Calcium On Murine Cytochrome C Release In Brain And Liver Mitochondria, Dane M. Edwards

Senior Honors Theses

A cell may use one of three main apoptotic pathways leading to programmed cell death: the extrinsic pathway, the perforin/granzyme pathway and the intrinsic pathway. The most pertinent to this discussion is the intrinsic pathway, which utilizes the mitochondria as an essential intermediary. Mitochondria’s primary function in relation to this pathway is the subsequent release of pro-apoptotic factors including cytochrome c, which activate a caspase cascade leading to the death of the cell. Cytochrome c is released partly due to an increase in cytosolic calcium levels. Two methods of the release of cytochrome c have been proposed. The first is …

The Effects Of Intermittent Isometric Fatigue On Concentric, Eccentric, And Isometric Torque, Robert W. Lewis Jr.

College of Education and Human Sciences: Dissertations, Theses, and Student Research

Fatiguing intermittent isometric (ISO) muscle actions of the leg extensors have been shown to result in a similar percent (%) decline in torque for concentric (CON), eccentric (ECC), and ISO muscle actions. However, the effects of intermittent ISO fatigue of the forearm flexors on CON, ECC, and ISO torque, have not been established. The purpose of this investigation was to determine the effects of 50 maximal, intermittent ISO forearm flexion muscle actions on CON, ECC, and ISO torque. Twenty adults (10 men (mean ± SD age = 21.9 ± 2.3 years) and 10 women (mean ± SD age = 22.7 …

Integrating Quantitative Experiments Into The Physiology Classroom, Sowmya Anjur

Faculty Publications & Research

Physiology and Disease is a student led inquiry based class at the Illinois Mathematics and Science Academy, where students design and execute their own experiments and analyze their data based on the evidence they have gathered. Student surveys have also indicated the need for more quantitation in lab experiments. To accommodate all these issues, several changes are being implemented into the course in an effort to allow students to identify the role of the neuronal controls for parameters such as blood pressure and heart rate, and to understand better how they work in concert. A new project (construction of a …

Improved Tolerance To Salt And Water Stress In Drosophila Melanogaster Cells Conferred By Late Embryogenesis Abundant Protein., Matthew Marunde, Dilini Samarajeewa, John Anderson, Shumin Li, Steven Hand, Michael Menze

Faculty Scholarship

Mechanisms that govern anhydrobiosis involve the accumulation of highly hydrophilic macromolecules, such as late embryogenesis abundant (LEA) proteins. Group 1 LEA proteins comprised of 181 (AfLEA1.1) and 197 (AfLEA1.3) amino acids were cloned from embryos of Artemia franciscana and expressed in Drosophila melanogaster cells (Kc167). Confocal microscopy revealed a construct composed of green fluorescence protein (GFP) and AfLEA1.3 accumulates in the mitochondria (AfLEA1.3-GFP), while AfLEA1.1-GFP was found in the cytoplasm. In the presence of mixed substrates, oxygen consumption was statistically identical for permeabilized Kc167 control and Kc167-AfLEA1.3 cells. Acute titrations of permeabilized cells with NaCl up to 500 mM led …

Small Interfering Rna-Mediated Translation Repression Alters Ribosome Sensitivity To Inhibition By Cycloheximide In Chlamydomonas Reinhardtii, Xinrong Ma

School of Biological Sciences: Dissertations, Theses, and Student Research

RNA interference (RNAi) is an evolutionarily conserved gene silencing mechanism in eukaryotes, with regulatory roles in a variety of biological processes, including cell cycle, cell differentiation, physiological and metabolic pathways, and stress responses. RNAi can function by transcriptional silencing, mRNA target cleavage, translation repression and/or DNA elimination. In this study, we used the unicellular green alga Chlamydomonas reinhardtii as a model system to study RNAi-mediated translation repression. We demonstrated that small RNAs (sRNAs) generated from exogenously introduced inverted repeat transgenes, with perfect complementarity to the 3’UTR of a target transcript, can inhibit protein synthesis, without or with only minimal mRNA …

Locating The Modifier Of Segregation Distorter In Drosophila Melanogaster, Samuel Craven

Honors Program Projects

The Drosophila melanogaster meiotic drive system Segregation Distorter (SD) has been a topic of great interest over the past decades due to its implications for fertility issues in fruit flies and other species as well. Several genes have been associated with this system; however, little research has focused on a particular one of these genes—the Modifier of SD. The location of this modifier gene is still unknown, so multiple deleted segments of DNA that compose a suspect area along the 2nd chromosome were tested here to see if some level of distortion is established in the absence of these segments. …

Derivation Of Multivariate Syndromic Outcome Metrics For Consistent Testing Across Multiple Models Of Cervical Spinal Cord Injury In Rats, Adam R. Ferguson, Karen-Amanda Irvine, John C. Gensel, Jessica L. Nielson, Amity Lin, Johnathan Ly, Mark R. Segal, Rajiv R. Ratan, Jacqueline C. Bresnahan, Michael S. Beattie

Physiology Faculty Publications

Spinal cord injury (SCI) and other neurological disorders involve complex biological and functional changes. Well-characterized preclinical models provide a powerful tool for understanding mechanisms of disease; however managing information produced by experimental models represents a significant challenge for translating findings across research projects and presents a substantial hurdle for translation of novel therapies to humans. In the present work we demonstrate a novel 'syndromic' information-processing approach for capitalizing on heterogeneous data from diverse preclinical models of SCI to discover translational outcomes for therapeutic testing. We first built a large, detailed repository of preclinical outcome data from 10 years of basic …

Teaching Physiology Online: Successful Use Of Case Studies In A Graduate Course, Giovanni Casotti, John T. Beneski, Maureen T. Knabb

Biology Faculty Publications

No abstract provided.

Excitatory Amino Acids Display Compartmental Disparity Between Plasma And Synovial Fluid In Clinical Arthropathies, Terry A. Mcnearney, Karin N. Westlund

Physiology Faculty Publications

BACKGROUND: Previous studies have demonstrated elevated levels of excitatory amino acids (EAA) glutamate (Glu) and aspartate (Asp) in the synovial fluid (SF) of patients with active arthritis. The source of SF EAA concentrations are thought in large part to be secondary to passive diffusion from the plasma across synovial membranes and less so, reflective of local synovial pathology.

OBJECTIVE: This descriptive report assesses the hypothesis that the SF EAA levels reflect inflammatory processes of the joint and are not dependent on plasma levels.

METHODS: Simultaneously drawn plasma and SF samples were obtained from 14 recently deceased cadavers and 10 patients …

Maintenance Of Mitochondrial Genomic Integrity In The Absence Of Manganese Superoxide Dismutase In Mouse Liver Hepatocytes., Anthony R. Cyr, Kyle E. Brown, Michael L. Mccormick, Mitchell C. Coleman, Adam J. Case, George S. Watts, Bernard W. Futscher, Douglas R. Spitz, Frederick E. Domann

Journal Articles: Cellular & Integrative Physiology

Manganese superoxide dismutase, encoded by the Sod2 gene, is a ubiquitously expressed mitochondrial antioxidant enzyme that is essential for mammalian life. Mice born with constitutive genetic knockout of Sod2 do not survive the neonatal stage, which renders the longitudinal study of the biochemical and metabolic effects of Sod2 loss difficult. However, multiple studies have demonstrated that tissue-specific knockout of Sod2 in murine liver yields no observable gross pathology or injury to the mouse. We hypothesized that Sod2 loss may have sub-pathologic effects on liver biology, including the acquisition of reactive oxygen species-mediated mitochondrial DNA mutations. To evaluate this, we established …

Release Of Avian Neurotensin In Response To Intraluminal Contents In The Duodenum Of Chickens, Teresa F. Degolier, Robert E. Carraway

Biological Sciences Faculty Publications

Peripheral and hepatic-portal plasma levels of neurotensin (NT) in fed and fasted chickens were determined using RIA. Portal levels of NT1-13 (fed = 61.3 ± 3.9 fmol/mL; fasted = 44.5 ± 3.9 fmol/mL) were significantly higher than peripheral levels (fed = 8.2 ± 3.3 fmol/mL; fasted = 7.8 ± 3.0 fmol/mL) collected from the wing vein, indicating that some NT is metabolized in the liver. Portal plasma levels of NT collected from fed birds were also significantly higher than portal plasma levels of NT collected from fasted birds. Neurotensin, as identified by HPLC, exhibited a 2-fold increase in plasma extracts …

The Impact Of Gut Passage By Binturongs (Arctictus Binturong) On Seed Germination, Christina P. Colon, Ahimsa Campos-Arceiz

Publications and Research

Binturongs (Arctictis binturong) are the largest of Asian civets and, due to their highly frugivorous diet, are expected to play an important role in seed dispersal processes. To study the effect of binturong gut passage on seed viability, we fed 10 captive binturongs with fruits of longan (Dimocarpus longan), papaya (Carica papaya) and chiku (Manilkara zapota), collected the seeds they defaecated, and planted these to determine seed germination rate and time. Of the defaecated seeds, 90.4% passed through binturong gut intact in under nine hours, and 99.4% passed in under 33 hours. Chiku seeds had the highest germination rate (35.7% …

The Feasibility Of A Fiber Optic Laser Approach To Relieving Lymphedematous Syndrome: A Case Report, Beniamino Palmieri, Alessandro Di Cerbo, Valentina Rottigni, Gregorio Fistetto, Tommaso Iannitti

Physiology Faculty Publications

Here we report a case of successful fiber optic laser treatment of lymphedema in a swollen arm post mastectomy. At the moment, this procedure has only anecdotal evidence to justify its use, but in our experience is a feasible, minimally invasive day-stay procedure which has been demonstrated to be safe and effective. Further nonhomogeneous case pooling and follow-up would enable guidelines and definite surgical protocols for its use to be implemented.

Seawater Flow Into The Digestive System Of Actinotroch Larvae (Phoronida), William Jaeckle

Scholarship

Actinotroch larva (Phoronida) concentrate and collect food particles during their planktonic existance. Reported mechanisms of particle capture include both ciliary reversal and direct interception along the larval tentacles, and suction of particle-containing seawater into the larval vestibule. These diverse mechanisms explain collection of particles, but not subsequent ingestion. Particle delivery into the digestive system is accomplished, at least in part, by the activity of the esophageal cilia. If and how the beat frequency of esophageal cilia is modified by the presence or absence of particulate or dissolved organic materials remains unknown for actinotroch larvae.

Systems Biology In Animal Breeding: Identifying Relationships Among Markers, Genes, And Phenotypes [Breeding And Genetics Symposium], John B. Cole, Ronald M. Lewis, C. Maltecca, S. Newman, K. M. Olson, R. G. Tait

Department of Animal Science: Faculty Publications

The Breeding and Genetics Symposium titled “Systems Biology in Animal Breeding: Identifying relationships among markers, genes, and phenotypes” was held at the Joint Annual Meeting of the American Society of Animal Science and the American Dairy Science Association in Phoenix, Arizona, July 15-19, 2012. The primary goal of the symposium was to demonstrate the use of high-density SNP genotypes to determine the complex regulatory relationships among genotypes and phenotypes but also to present methods for studying complex relationships among phenotypes. Case studies from mammalian and avian species were included to emphasize the broad applicability of these methods.

Cardiovascular Fitness Associated With Cognitive Performance In Heart Failure Patients Enrolled In Cardiac Rehabilitation, Sarah Garcia, Michael L. Alosco, Mary Beth Spitznagel, Ronald Cohen, Naftali Raz, Lawrence Sweet, Richard Josephson, Joel Hughes, Jim Rosneck, Morgan L. Oberle, John Gunstad

Wayne State University Associated BioMed Central Scholarship

Abstract

Background

Reduced cognitive function is common in persons with heart failure (HF). Cardiovascular fitness is a known contributor to cognitive function in many patient populations, but has only been linked to cognition based on estimates of fitness in HF. The current study examined the relationship between fitness as measured by metabolic equivalents (METs) from a standardized stress test and cognition in persons with HF, as well as the validity of office-based predictors of fitness in this population.

Methods

Forty-one HF patients enrolled in cardiac rehabilitation completed a standardized exercise stress test protocol, a brief neuropsychological battery, the 2-minute step …

Androgen Receptor-Target Genes In African American Prostate Cancer Disparities, Bi-Dar Wang, Qi Yang, Kristin Ceniccola, Fernando Bianco, Ramez Andrawis, Thomas W. Jarrett, Harold A. Frazier, Steven R. Patierno, Norman H. Lee

Pharmacology and Physiology Faculty Publications

The incidence and mortality rates of prostate cancer (PCa) are higher in African American (AA) compared to Caucasian American (CA) men. To elucidate the molecular mechanisms underlying PCa disparities, we employed an integrative approach combining gene expression profiling and pathway and promoter analyses to investigate differential transcriptomes and deregulated signaling pathways in AA versus CA cancers. A comparison of AA and CA PCa specimens identified 1,188 differentially expressed genes. Interestingly, these transcriptional differences were overrepresented in signaling pathways that converged on the androgen receptor (AR), suggesting that the AR may be a unifying oncogenic theme in AA PCa. Gene promoter …

Euryhalinity In An Evolutionary Context, Eric T. Schultz, Stephen D. Mccormick

EEB Articles

This chapter focuses on the evolutionary importance and taxonomic distribution of euryhalinity. Euryhalinity refers to broad halotolerance and broad halohabitat distribution. Salinity exposure experiments have demonstrated that species vary tenfold in their range of tolerable salinity levels, primarily because of differences in upper limits. Halotolerance breadth varies with the species’ evolutionary history, as represented by its ordinal classification, and with the species’ halohabitat. Freshwater and seawater species tolerate brackish water; their empirically-determined fundamental haloniche is broader than their realized haloniche, as revealed by the halohabitats they occupy. With respect to halohabitat distribution, a minority of species (<10%) are euryhaline. Habitat-euryhalinity is prevalent among basal actinopterygian fishes, is largely absent from orders arising from intermediate nodes, and reappears in the most derived taxa. There is pronounced family-level variability in the tendency to be halohabitat-euryhaline, which may have arisen during a burst of diversification following the Cretaceous-Palaeogene extinction. Low prevalence notwithstanding, euryhaline species are potent sources of evolutionary diversity. Euryhalinity is regarded as a key innovation trait whose evolution enables exploitation of new adaptive zone, triggering cladogenesis. We review phylogenetically-informed studies that demonstrate freshwater species diversifying from euryhaline ancestors through processes such as landlocking. These studies indicate that some euryhaline taxa are particularly susceptible to changes in halohabitat and subsequent diversification, and some geographic regions have been hotspots for transitions to freshwater. Comparative studies on mechanisms among multiple taxa and at multiple levels of biological integration are needed to clarify evolutionary pathways to, and from, euryhalinity.

Age-Associated Metabolic And Morphologic Changes In Mitochondria Of Individual Mouse And Hamster Oocytes, Fatma Simsek-Duran, Fang Li, Wentia Ford, R. James Swanson, Howard W. Jones Jr., Frank J. Castora

Biological Sciences Faculty Publications

Background: In human oocytes, as in other mammalian ova, there is a significant variation in the pregnancy potential, with approximately 20% of oocyte-sperm meetings resulting in pregnancies. This frequency of successful fertilization decreases as the oocytes age. This low proportion of fruitful couplings appears to be influenced by changes in mitochondrial structure and function. In this study, we have examined mitochondrial biogenesis in both hamster (Mesocricetus auratus) and mouse (Mus musculus) ova as models for understanding the effects of aging on mitochondrial structure and energy production within the mammalian oocyte.

Methodology/Principal Findings: Individual metaphase …

Functional Effects Of Kcnq K(+) Channels In Airway Smooth Muscle, Alexey I. Evseev, Iurii Semenov, Crystal R. Archer, Jorge L. Medina, Peter H. Dube, Mark S. Shapiro, Robert Brenner

Bioelectrics Publications

KCNQ (Kv7) channels underlie a voltage-gated K+ current best known for control of neuronal excitability, and its inhibition by Gq/11-coupled, muscarinic signaling. Studies have indicated expression of KCNQ channels in airway smooth muscle (ASM), a tissue that is predominantly regulated by muscarinic receptor signaling. Therefore, we investigated the function of KCNQ channels in rodent ASM and their interplay with Gq/11-coupled M3 muscarinic receptors. Perforated-patch clamp of dissociated ASM cells detected a K+ current inhibited by the KCNQ antagonist, XE991, and augmented by the specific agonist, flupirtine. KCNQ channels begin to activate at voltages near resting potentials for ASM cells, and …

Developmental Changes In Postural Stability During The Performance Of A Precision Manual Task, Jeffrey M. Haddad, Laura J. Claxton, Dawn Melzer, Joseph Hamill, Richard E. A. Van Emmerik

Psychology Faculty Publications

Posture becomes integrated with other goal-directed behaviors early in infancy and continues to develop into the second decade of life. However, the developmental time course over which posture is stabilized relative to the base of support during a dynamic manual precision task has not been examined. Postural-manual integration was assessed in 7-year-olds, 10-year-olds, and adults using a postural-manual task in which task precision (target fitting size) and postural difficulty (reaching distance to a target) were manipulated. The main dependent variable was postural time-to-contact (TtC). Results indicated systematic age effects in which TtC was shortest in the 7-year-olds, increased in the …