Groups of passive and active control state in longitudinal experiments: an electrophysiological study

Long-term electrophysiological experiments were carried out with rats with chronically implanted electrodes into dopaminergic brain structures. Within 4 weeks after surgery, the relative spectral power of electrical activity in the delta1 and delta2 frequency bands decreased, while the relative spectral power in the alpha, beta1 and beta2 bands increased. A delayed (to the 4-5th week after surgery) increase in the total amount of sleep and REM sleep percent was observed in the sleep architecture of these animals. Multiple (during 2 weeks daily) intraperitoneal saline injections altered the dynamic of electrophysiological indices on the 2nd-3rd postsurgery weeks. The total sleep amount being not increased, the total and mean REM sleep durations increased, and the dynamic of the relative spectral power of electrical activity in the dopaminergic brain structures in the delta1, alpha and beta2 bands was found to be changed.     

Neural network detected in a presumed vestigial trait: ultrastructure of the salmonid adipose fin

A wide variety of rudimentary and apparently non-functional traits have persisted over extended evolutionary time. Recent evidence has shown that some of these traits may be maintained as a result of developmental constraints or neutral energetic cost, but for others their true function was not recognized. The adipose fin is small, fleshy, non-rayed and located between the dorsal and caudal fins on eight orders of basal teleosts and has traditionally been regarded as vestigial without clear function. We describe here the ultrastructure of the adipose fin and for the first time, to our knowledge, present evidence of extensive nervous tissue, as well as an unusual subdermal complex of interconnected astrocyte-like cells equipped with primary cilia. The fin contains neither adipose tissue nor fin rays. Many fusiform actinotrichia, comprising dense striated macrofibrils, support the free edge and connect with collagen cables that link the two sides. These results are consistent with a recent hypothesis that the adipose fin may act as a precaudal flow sensor, where its removal can be detrimental to swimming efficiency in turbulent water. Our findings provide insight to the broader themes of function versus constraints in evolutionary biology and may have significance for fisheries science, as the adipose fin is routinely removed from millions of salmonids each year.     

Evaluation of the roles of passive and active control of balance using a balance control model

At present there is a lack of consensus regarding the relative roles of passive and active control of quiet upright stance. In the current work, this issue was investigated using two simulation models based on contemporary theories. Specifically, the two models, both of which assumed active control torques to be generated from an optimal neural controller, differed with respect to whether or not passive control torques (stiffness and damping) were included. Model parameters were specified using experimental center-of-pressure (COP) time series obtained during upright stance, and comparisons then made between simulated and actual COP-based measures. Including both active and passive joint torques in the control model did not appear to lead to any improvement in the ability to simulate COP compared with only including active joint torque. Further, simulated passive control torques were typically less than 10% of the active control torques, though some exceptions were found. These results, along with existing empirical evidence, suggest that active control torque is dominant in maintaining balance during upright stance.     

Active follow-up versus passive linkage with cancer registries for case ascertainment in a cohort

BackgroundAscertaining incident cancers is a critical component of cancer-focused epidemiologic cohorts and of cancer prevention trials. Potential methods: for cancer case ascertainment include active follow-up and passive linkage with state cancer registries. Here we compare the two approaches in a large cancer screening trial.MethodsThe Prostate, Lung, Colorectal and Ovarian (PLCO) cancer screening trial enrolled 154,955 subjects at ten U.S. centers and followed them for all-cancer incidence. Cancers were ascertained by an active follow-up process involving annual questionnaires, retrieval of records and medical record abstracting to ascertain and confirm cancers. For a subset of centers, linkage with state cancer registries was also performed. We assessed the agreement of the two methods in ascertaining incident cancers from 1993 to 2009 in 80,083 subjects from six PLCO centers where cancers were ascertained both by active follow-up and through linkages with 14 state registries.ResultsThe ratio (times 100) of confirmed cases ascertained by registry linkage compared to active follow-up was 96.4 (95% CI: 95.1–98.2). Of cancers ascertained by either method, 86.6% and 83.5% were identified by active follow-up and by registry linkage, respectively. Of cancers missed by active follow-up, 30% were after subjects were lost to follow-up and 16% were reported but could not be confirmed. Of cancers missed by the registries, 27% were not sent to the state registry of the subject’s current address at the time of linkage.ConclusionLinkage with state registries identified a similar number of cancers as active follow-up and can be a cost-effective method to ascertain incident cancers in a large cohort.     

The musculoskeletal system of the caudal fin in basal Actinopterygii: heterocercy,diphycercy, homocercy

The caudal fin represents the posteriormost region of the vertebrate axis and is one location where forces are exerted to the surrounding medium. The evolutionary changes of its skeleton have been well analyzed in gnathostomes and revealed transitions from heterocercal to diphycercal and homocercal tails. In contrast, we only know little about the evolutionary transformations of the muscular system of the caudalis and about possible ways of force transmission from anterior myomeres to the caudal fin. The goals of this study are to gain insight into evolutionary transformations of the musculoskeletal system in the four basal actinopterygian groups (Cladistia, Chondrostei, Ginglymodi, and Halecomorphi) and to identify likely pathways of force transmission to the tail. In this context, the connective tissue of the myosepta is considered to be an essential part of the musculoskeletal system. For the first time, this system is analyzed for the whole postanal region. The use of microdissection techniques and polarized light microscopy revealed the collagen fiber architecture and the insertions of all postanal myosepta from cleared and stained specimens. The collagen fiber architecture is similar in all investigated specimens and thus represents the primary actinopterygian condition. All parts of postanal myosepta are dominated by longitudinally arranged myoseptal tendons (lateral and myorhabdoid tendons) that span several vertebral segments. This architecture supports the view that posterior myosepta are well designed to transfer muscular forces that are generated in anterior myomeres. In contrast to the uniform myoseptal architecture, the musculoskeletal system differs between the four basal actinopterygian groups. Among them, chondrosteans have retained the plesiomorphic condition of actinopterygian tails. For the remaining taxa several evolutionary novelties in the musculoskeletal system of the tail are revealed. Most of these have evolved independently in the cladistian and neopterygian stem lineage. In these groups extensions of all epaxial and hypaxial parts of myosepta are present that insert on caudal fin rays. This remarkable contribution of epaxial muscle masses to the caudal fin organization is in contrast to the skeletal organization, that largely derives from hypaxial material only. In contrast to former studies the hypochordal longitudinalis muscle is shown to be a synapomorphy of Halecostomi (Halecomorphi + Teleostei). The morphological framework presented here allows to generate new hypotheses on the function of caudal fins that can be tested experimentally.     

First evidence of wasp brood development inside active nests of a termite with the description of a previously unknown potter wasp species

Potter wasps (Vespidae: Eumeninae) are known to exhibit not only sophisticated preying strategies but also a remarkable ability to manipulate clay during nest building. Due to a mixture of plasticity in building behavior and flexibility in substrate preferences during nest building, the group has been reported nesting in a variety of places, including decaying nests abandoned by termite species. Yet, evidence of wasps nesting inside senescent termite mounds is poorly reported, and to date, accounts confirming their presence inside active colonies of termites are absent. Here, we address a novel intriguing association between two species from the Brazilian Cerrado: a previously unknown potter wasp (nest invader) and a termite species (nest builder). Besides scientifically describing Montezumia termitophila sp. nov. (Vespidae: Eumeninae), named after its association with the termite Constrictotermes cyphergaster (Silvestri, 1901) (Termitidae: Nasutitermitinae), we provide preliminary information about the new species'' bionomics by including (a) a hypothetical life cycle based on the evidence we collected and (b) a footage showing the first interaction between a recently ecloded wasp and a group of termites. In doing so, we attempt to provoke relevant discussions in the field and, perhaps, motivate further studies with the group. Finally, we describe a solution to efficiently detect and sample termitophilous species from termite nests, an intrinsic yet challenging task of any studies dealing with such a cryptic biological system.     

Models of passive and active dendrite motoneuron pools and their differences in muscle force control

Motoneuron (MN) dendrites may be changed from a passive to an active state by increasing the levels of spinal cord neuromodulators, which activate persistent inward currents (PICs). These exert a powerful influence on MN behavior and modify the motor control both in normal and pathological conditions. Motoneuronal PICs are believed to induce nonlinear phenomena such as the genesis of extra torque and torque hysteresis in response to percutaneous electrical stimulation or tendon vibration in humans. An existing large-scale neuromuscular simulator was expanded to include MN models that have a capability to change their dynamic behaviors depending on the neuromodulation level. The simulation results indicated that the variability (standard deviation) of a maintained force depended on the level of neuromodulatory activity. A force with lower variability was obtained when the motoneuronal network was under a strong influence of PICs, suggesting a functional role in postural and precision tasks. In an additional set of simulations when PICs were active in the dendrites of the MN models, the results successfully reproduced experimental results reported from humans. Extra torque was evoked by the self-sustained discharge of spinal MNs, whereas differences in recruitment and de-recruitment levels of the MNs were the main reason behind torque and electromyogram (EMG) hysteresis. Finally, simulations were also used to study the influence of inhibitory inputs on a MN pool that was under the effect of PICs. The results showed that inhibition was of great importance in the production of a phasic force, requiring a reduced co-contraction of agonist and antagonist muscles. These results show the richness of functionally relevant behaviors that can arise from a MN pool under the action of PICs.     

Democratization in a passive dendritic tree: an analytical investigation

One way to achieve amplification of distal synaptic inputs on a dendritic tree is to scale the amplitude and/or duration of the synaptic conductance with its distance from the soma. This is an example of what is often referred to as "dendritic democracy". Although well studied experimentally, to date this phenomenon has not been thoroughly explored from a mathematical perspective. In this paper we adopt a passive model of a dendritic tree with distributed excitatory synaptic conductances and analyze a number of key measures of democracy. In particular, via moment methods we derive laws for the transport, from synapse to soma, of strength, characteristic time, and dispersion. These laws lead immediately to synaptic scalings that overcome attenuation with distance. We follow this with a Neumann approximation of Green's representation that readily produces the synaptic scaling that democratizes the peak somatic voltage response. Results are obtained for both idealized geometries and for the more realistic geometry of a rat CA1 pyramidal cell. For each measure of democratization we produce and contrast the synaptic scaling associated with treating the synapse as either a conductance change or a current injection. We find that our respective scalings agree up to a critical distance from the soma and we reveal how this critical distance decreases with decreasing branch radius.     

Dual roles of the A kinase-anchoring protein Yotiao in the modulation of a cardiac potassium channel: a passive adaptor versus an active regulator

Cardiac function is regulated critically by the autonomic nervous system to adapt to the physical activity and emotional stress. A slowly activating cardiac potassium channel (I(Ks)) is modulated by stimulation of the sympathetic nervous system (SNS) and contributes to cardiac action potential shortening in the face of concomitant increases in heart rate. Activation of beta-adrenergic receptors in response to SNS stimulation results in protein kinase A (PKA)-mediated phosphorylation of I(Ks) channels. We have found that the functional regulation of the I(Ks) channel by PKA requires the A kinase-anchoring protein (AKAP) Yotiao. Yotiao forms a macromolecular complex with the channel and recruits key enzymes such as PKA and protein phosphatase 1 (PP1) to control the phosphorylation state of I(Ks). Our recent findings revealed a more active role of Yotiao in the PKA modulation of I(Ks). We found that Yotiao participates actively in translating the phosphorylation-induced change into altered channel activity. Moreover Yotiao itself can be phosphorylated by PKA upon beta-adrenergic stimulation. Ablation of Yotiao phosphorylation impairs PKA-induced changes in I(Ks) voltage-dependent activation and current kinetics. Taken together we have evidence to suggest that Yotiao plays dual roles in the PKA modulation of the I(Ks) channel. It acts not only as an adaptor protein to coordinate enzymatic reactions but also as an active regulator that directly affects channel function.     

On a three–dimensional model for the description of the passive characteristics of skeletal muscle tissue

In this work, a three–dimensional model was developed to describe the passive mechanical behaviour of anisotropic skeletal muscle tissue. To validate the model, orientation–dependent axial (\(0^\circ\), \(45^\circ\), \(90^\circ\)) and semi–confined compression experiments (mode I, II, III) were performed on soleus muscle tissue from rabbits. In the latter experiments, specimen deformation is prescribed in the loading direction and prevented in an additional spatial direction, fibre compression at \(0^\circ\) (mode I), fibre elongation at \(90^\circ\) (mode II) and a neutral state of the fibres at \(90^\circ\) where their length is kept constant (mode III). Overall, the model can adequately describe the mechanical behaviour with a relatively small number of model parameters. The stiffest tissue response during orientation–dependent axial compression (\(-\,7.7\,\pm \,1.3\) kPa) occurs when the fibres are oriented perpendicular to the loading direction (\(90^\circ\)) and are thus stretched during loading. Semi–confined compression experiments yielded the stiffest tissue (\(-\,36.7\,\pm \,11.2\) kPa) in mode II when the muscle fibres are stretched. The extensive data set collected in this study allows to study the different error measures depending on the deformation state or the combination of deformation states.

     

Identification of potential neuromotor mechanisms of manual therapy in patients with musculoskeletal disablement: rationale and description of a clinical trial

Background  

Many health care practitioners use a variety of hands-on treatments to improve symptoms and disablement in patients with musculoskeletal pathology.     

First description of betalains biosynthesis in an aquatic organism: characterization of 4,5-DOPA-extradiol-dioxygenase activity in the cyanobacteria Anabaena cylindrica

The biosynthesis of betalamic acid, the structural unit of pigments betalains, is performed by enzymes with 4,5-DOPA-extradiol-dioxygenase activity. These enzymes were believed to be limited to plants of the order Caryophyllales and to some fungi. However, the discovery of Gluconacetobacter diazotrophicus as the first betalain-forming bacterium opened a new field in the search for novel biological systems able to produce betalains. This paper describes molecular and functional characterization of a novel dioxygenase enzyme from the aquatic cyanobacterium Anabaena cylindrica. The enzyme was found to be a homodimer of a polypeptide of 17.8 kDa that, opposite to previous related enzymes, showed a strong inhibition by excess of the precursor L-DOPA. However, its heterologous expression has allowed detecting the formation of the main compounds in the biosynthetic pathway of betalains. In addition, phylogenetic analysis has shown that this enzyme is not close related to enzymes from plants, fungi or proteobacteria such as G. diazotrophicus. The presence of enzymes that produce these health-promoting compounds is more diverse than expected. The discovery of this novel dioxygenase in the phylum cyanobacteria expands the presence of betalamic acid-forming enzymes in organisms of different nature with no apparent relationship among them.     

AMPK, an active player in the control of metabolism

Impairment in the regulation of energy homeostasis and imbalance between energy intake and energy expenditure lead to many metabolic disorders and diseases such as obesity and type 2 diabetes. AMP-activated protein kinase (AMPK) is considered as a "fuel-gauge" in the cell and plays a key role in the regulation of energy metabolism. Activated by an increase in the AMP/ATP ratio, AMPK switches on catabolic pathways such as fatty acid oxidation and switches off anabolic pathways such as lipogenesis or gluconeogenesis. Insulin-sensitizing adipokines (leptin and adiponectin) and anti-diabetic drugs (thiazolidinediones and biguanides) are acting in part through the activation of AMPK. More recent findings indicate that AMPK plays also a major role in the control of whole body energy homeostasis by integrating, at the hypothalamus level, nutrient and hormonal signals that regulate food intake and energy expenditure. AMPK provides therefore a potential target for the treatment of metabolic diseases such as obesity and type II diabetes.