The neuropeptide red pigment concentrating hormone affects rhythmic pattern generation at multiple sites

The level of LamB protein in the outer membrane of Escherichia coli was derepressed in the absence of a known inducer (maltodextrins) under carbohydrate-limiting conditions in chemostats. LamB protein contributed to the ability of the bacteria to remove sugar from glucose-limited chemostats, and well-characterized lamB mutants with reduced stability constants for glucose were less growth competitive under glucose limitation than those with wild-type affinity. In turn, wild-type bacteria were less growth competitive than lamB mutants with enhanced sugar affinity. In contrast to an earlier report, we found that LamB- bacteria were less able to compete in carbohydrate-limited chemostats (with glucose, lactose, arabinose, or glycerol as the carbon and energy sources) when mixed with LamB+ bacteria. The transport Km for [14C]glucose was affected by the presence or affinity of LamB, but only in chemostat-grown bacteria, with their elevated LamB levels. The pattern of expression of LamB and the advantage it confers for growth on low concentrations of carbohydrates are consistent with a wider role in sugar permeation than simply maltosaccharide transport, and hence the well-known maltoporin activity of LamB is but one facet of its role as the general glycoporin of E. coli. A corollary of these findings is that OmpF/OmpC porins, present at high levels in carbon-limited bacteria, do not provide sufficient permeability to sugars or even glycerol to support high growth rates at low concentrations. Hence, the sugar-binding site of LamB protein is an important contributor to the permeability of the outer membrane to carbohydrates in habitats with low extracellular nutrient concentrations.     

Respiration mechanics in tetraplegia

Patients with quadriplegia due to transection of the lower cervical cord show, on spirographic examination, a marked decrease in vital capacity and its two components, i.e. inspiratory capacity (i.c.) and expiratory reserve volume (ERV). The loss of IC results partly from the decreased inspiratory muscle strength consecutive to the intercostal muscle paralysis but mostly from a reduction in the distensibility of the lungs and the rib cage. The reduction in ERV is related to the paralysis of all the well-recognized muscles of expiration (abdominals, interosseous internal intercostals); however, the clavicular portion of the pectoralis major allows these patients to maintain a small ERV.     

Organization of the circadian system in insects

The circadian systems of different insect groups are summarized and compared. Emphasis is placed on the anatomical identification and characterization of circadian pacemakers, as well as on their entrainment, coupling, and output pathways. Cockroaches, crickets, beetles, and flies possess bilaterally organized pacemakers in the optic lobes that appear to be located in the accessory medulla, a small neuropil between the medulla and the lobula. Neurons that are immunoreactive for the peptide pigment-dispersing hormone (PDH) arborize in the accessory medulla and appear to be important components of the optic lobe pacemakers. The neuronal architecture of the accessory medulla with associated PDH-immunoreactive neurons is best characterized in cockroaches, while the molecular machinery of rhythm generation is best understood in fruit flies. One essential component of the circadian clock is the period protein (PER), which colocalizes with PDH in about half of the fruit fly's presumptive pacemaker neurons. PER is also found in the presumptive pacemaker neurons of beetles and moths, but appears to have different functions in these insects. In moths, the pacemakers are situated in the central brain and are closely associated with neuroendocrine functions. In the other insects, neurons associated with neuroendocrine functions also appear to be closely coupled to the optic lobe pacemakers. Some crickets and flies seem to possess central brain pacemakers in addition to their optic lobe pacemakers. With respect to neuronal organization, the circadian systems of insects show striking similarities to the vertebrate circadian system.     

Age-specific problems in rhythmic timing.

The authors investigated performance in 2 rhythm tasks in young (M?=?23.8 years) and older (M?=?71.4 years) amateur pianists to test whether slowing of a central clock can explain age-related changes in timing variability. Successive keystrokes in the rhythm tasks were separated by either identical (isochronous) time intervals or varying (anisochronous) intervals. Variability was comparable for young and older adults in the isochronous task; pronounced age effects were found for the anisochronous rhythm. Analyses of covariances between intervals rule out slowing of a central clock as an explanation of the findings, which instead support the distinction between target specification, timekeeper execution, and motor implementation proposed by the rhythm program hypothesis (D. Vorberg & A. M. Wing, 1996). Age stability was found at the level of motor implementation, but there were age-related deficits for processes related to target-duration specification. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Handedness and the asymmetric dynamics of bimanual rhythmic coordination.

Human handedness was investigated in a 1:1 interlimb rhythmic coordination in which consistent and inconsistent left-handed and right-handed individuals oscillated hand-held pendulums. Mean phase difference (φstable) and its standard deviation (SDφ) were evaluated as functions of mode of coordination (in-phase vs anti-phase) and the symmetry conditions imposed by controlling the natural frequencies of the left and right pendulums. The dependencies of φstable and SDφ on coordination mode and imposed symmetry were found to be systematically affected by handedness. The data were consistent with an elaboration of the established order parameter dynamics of interlimb rhythmic coordination. The elaboration includes additional 27π periodic terms that break the symmetry of those dynamics when the natural frequencies of the component rhythmic units are identical. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Respiration and oxidative phosphorylation in the apicomplexan parasite Toxoplasma gondii

Respiration, oxidative phosphorylation, and the mitochondrial membrane potential (DeltaPsi) of tachyzoites of the apicomplexan parasite Toxoplasma gondii were assayed in situ using very low concentrations of digitonin to render their plasma membrane permeable to succinate, ADP, safranin O, and other small molecules. The rate of basal respiration was slightly increased by digitonin when the cells were incubated in medium containing succinate. ADP promoted an oligomycin-sensitive transition from resting to phosphorylating respiration. Respiration was sensitive to antimycin A and cyanide, and N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) was oxidized by antimycin A-poisoned mitochondria. The addition of ADP after TMPD/ascorbate also resulted in phosphorylating respiration. The antitoxoplasmosis drug atovaquone, at a very low concentration (0.03 microM), totally inhibited respiration and disrupted the mitochondrial membrane potential. Atovaquone was shown to inhibit the respiratory chain of T. gondii and mammalian mitochondria between cytochrome b and c1 as occurs with antimycin A1. Phosphorylation of ADP could not be obtained in permeabilized tachyzoites in the presence of either pyruvate, 3-oxo-glutarate, glutamate, isocitrate, dihydroorotate, alpha-glycerophosphate, or endogenous substrates. Although ADP phosphorylation was detected in the presence of malate, this activity was rotenone-insensitive and was probably due to the conversion of malate into succinate through a fumarate reductase activity that was detected in mitochondrial extracts. Together these results provide the first direct biochemical evidence that the respiratory chain and oxidative phosphorylation are functional in apicomplexan parasites, although the terminal respiratory pathway is different from that in the mammalian host.     

Fluctuations and phase symmetry in coordinated rhythmic movements.

Investigated the assertion that pendular, clocking movements typify mammalian terrestrial locomotion, using a procedure in which people swing hand-held pendulums at the wrists, comfortably and rhythmically. Previous work by P. N. Kugler and the 2nd author (1986) suggests that the periodic timing and powering of rhythmic movements in the comfort state follow from different laws. One law guides the assembling of the reference frame for clocking. Another law guides the assembling of the muscular, escapement processes determining the cycle energy. Pendular, clocking behavior was examined in 4 adult males for in-phase and out-of-phase coordinations. A. M. Wing and A. B. Kristofferson's (see record 1974-08195-001) method for parsing periodic-timing variance into independent clock and motor sources was applied. Results show that mean periodicity was unaffected by phase. Clock fluctuations, however, were larger out of phase than in phase. Motor fluctuations were indifferent to phase but reflected the departures of individual wrist-pendulum systems from their preferred periods. It is suggested that an intended phase relation is realized as a constraint on clock states. These states are more stable under the in-phase constraint than under the out-of-phase constraint. (36 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The formation of the karyosphere in the oogenesis of insects and amphibians

This review deals with the authors' own and literary data on the ultrastructural and cytochemical organization of insect and amphibian oocyte nuclei, with special attention being paid to the karyosphere and its capsule. The evidence provided is supplemented with data on isolated karyospheres in Rana temporaria oocytes. A conclusion is made that the karyosphere is a complex structure which contains all chromosomes in the limited space of the oocyte nucleus, and that these chromosomes are, as a rule, in the process of inactivation. It is inferred that the karyosphere capsule commonly appears in gigantic oocyte nuclei (more than 100 micron in diameter) containing extrachromosomal DNA. The analogy of capsule organization in different invertebrate and vertebrate species is discussed, in addition to the involvement of presumably homologous nuclear structures (e.g. derivatives of synaptonemal complexes and nuclear envelope) in capsule formation. It is assumed that the karyosphere capsule is a specially organized part of the nuclear matrix. The capsule provides nuclear compartmentalization and chromosome localization in the germinal vesicle. Studies of this sort open up new possibilities to further investigation of intranuclear morphogenesis.     

Improving leaping ability in elite rhythmic gymnasts

PURPOSE: The purpose of this study was to improve the leaping ability of athletes in rhythmic gymnastics, a high leap demanding sport, using a controlled course of jump training. METHODS: Six elite athletes underwent a course of leap training including pool training and Pilates' Method of Body Conditioning using spring controlled resistance to muscular exertion. Baseline data was obtained on a force plate that measured reaction time, leap height, and explosive power on each athlete before initiating training. RESULTS: After 1 month of training, leap height improved 16.2%, ground reaction time improved 50%, and explosive power improved 220%. With continued maintenance training, no decrease in effect was noted; however, no significant improvement occurred after the first month of training. At 1 yr with discontinuation of the leaping protocol but continued training within the sport, the initial gains were likewise maintained. No injuries occurred during participation in the leaping protocol. CONCLUSIONS: Elite rhythmic gymnasts can safely improve their leaping ability significantly through an intense course of jump training. Continued training with the leaping protocol does not appear to further enhance the benefit; however, the gains appear to be maintained at 4 months and 1 yr post training with or without additional training with the leaping protocol.     

Temporal constraints in processing of nonverbal rhythmic patterns

This study investigates the effect of a mental content of presented stimuli, normal aging and individual differences in cognitive abilities on temporal limits of an integration mechanism. Younger and older subject grouped together the beats generated by a metronome. Subjects were asked to listen to the beats of a metronome and to accentuate mentally every second, third, fourth...etc. beat, to create a subjective rhythm. This rhythm exists, in fact, only in subjects' mind and not objectively. Subjects reported verbally how many clicks they were able to integrate into a perceptual unit. On this basis, the time interval during which subjects were able to integrate temporally separated stimuli was calculated (number of beats reported as being integrated x time distance between beats) for different metronome frequencies. The results show, firstly, that the length of integration periods significantly depends on the frequency of presented metronome beats. When the frequency of metronome beats is high, the time interval during which the subjects integrate beats into a single perceptual unit is shorter. Secondly, older adults integrate information during a longer time interval than younger ones. Thirdly, the length of an integration period is related to a subjects' level of cognitive ability. These results suggest that the length of an integration period is not a constant, stable feature, but varies across the life span depending on the mental content of the information presented and individual factors.     

Upper airway motor outputs during vomiting versus swallowing in the decerebrate cat

Hair cells in the basilar papilla of birds have the capacity to regenerate after injury. Methods commonly used to induce cochlear damage are systemic application of ototoxic substances such as aminoglycoside antibiotics or loud sound. Both methods have disadvantages. The systemic application of antibiotics results in damage restricted to the basal 50% of the papilla and has severe side effects on the kidneys. Loud sound damages only small parts of the papilla and is restricted to the short hair cells. The present study was undertaken to determine the effect of local aminoglycoside application on the physiology and morphology of the avian basilar papilla. Collagen sponges loaded with gentamicin were placed at the round window of the cochlea in adult pigeons. The time course of hearing thresholds was determined from auditory brain stem responses elicited with pure tone bursts within a frequency range of 0.35-5.565 kHz. The condition of the basilar papilla was determined from scanning electron micrographs. Five days after application of the collagen sponges loaded with gentamicin severe hearing loss, except for the lowest frequency tested, was observed. Only at the apical 20% of the basilar papilla hair cells were left intact, all other hair cells were missing or damaged. At all frequencies there was little functional recovery until day 13 after implantation. At frequencies above 1 kHz functional recovery occurred at a rate of up to 4 dB/day until day 21, beyond that day recovery continued at a rate below 1 dB/day until day 48 at the 5.6 kHz. Below 1 kHz recovery occurred up to day 22, the recovery rate was below 2 dB/day. A residual hearing loss of about 15-25 dB remained at all frequencies, except for the lowest frequency tested. At day 20 new hair cells were seen on the basilar papilla. At day 48 the hair cells appeared to have recovered fully, except for the orientation of the hair cell bundles. The advantage of the local application of the aminoglycoside drug over systemic application is that it damages almost all hair cells in the basilar papilla and it has no toxic side effects. The damage is more extensive than with systemic application.     

Environmental coupling modulates the attractors of rhythmic coordination.

A simple instance of coupling behavior to the environment is oscillating the hands in pace with metronome beats. This environmental coupling can be weaker (1 beat per cycle) or stronger (2 beats per cycle). The authors examined whether strength of environmental coupling enhanced the stability of in-phase bimanual coordination. Detuning by manipulanda that produced different left and right eigenfrequencies shifted the relative phase angle from 0°, with the size of the shift larger for higher movement frequencies. Stronger environmental coupling was found to decrease this relative-phase shift, with accompanying increase and reduction, respectively, in recurrence quantification measures related to coordination stability and coordination noise. Stronger environmental coupling also increased oscillation amplitude. Results are considered from the perspective of parametric stabilization. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

The evolution of hexamerins and the phylogeny of insects

The impact of group discussion on the decision-making effectiveness of medical teams was examined. Three-person teams of physicians diagnosed 2 hypothetical medical cases. Some of the information about each case was given to all team members prior to discussion (shared information), whereas the rest was divided among them (unshared information). Compared with unshared information, shared information was more likely to be pooled during discussion and was pooled earlier. In addition, team leaders were consistently more likely than other members to ask questions and to repeat shared information and, over time, also became more likely than others to repeat unshared information. Finally, pooling unshared (but not shared) information improved the overall accuracy of the team diagnoses, whereas repeating both shared and unshared information affected bias (but not accuracy) in the diagnoses.     

Occurrence and function of a proteinase inhibitor in the hemolymph of insects

The presence of proteinase inhibitor has been proved in the hemolymph of a number of insect species from seven different insect orders. The amount of proteinase inhibitor in the hemolymph significantly increases after injection of inactivated bacteria into the hemocoelom of Galleria mellonella-larvae. Moreover the larvae show an increased resistance against normally lethal concentrations of trypsin, chymotrypsin, pronase P and extracellular proteinase produced by Pseudomonas aeruginosa. It is discussed that the proteinase inhibitor is one of the factors acting in the antibacterial defense system in the hemolymph of Galleria mellonella-larvae.     

Temporal rescaling of simple and complex ratios in rhythmic tapping.

Two well-established phenomena in temporal performance—preference for simple ratios over complex ratios and the ability to proportionately rescale temporal patterns—were examined together. Unlike the case with simple ratios, participants (3 trained musicians) showed only a limited ability to learn complex ratios and no ability to proportionately rescale them. These differences suggest that different mechanisms are used to produce the 2 ratio types. Systematic biases observed in the performances of the simple ratios (6 trained musicians) were modeled by assuming that an additive timing component, which is unequal for short and long intervals and changes with base rate, overlays a system that preferentially produces simple ratios. The general pattern of results was consistent with the view that rhythmic learning builds on or modifies a system of innate preferences. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Vasodilation contributes to the rapid hyperemia with rhythmic contractions in humans

The hypothesis that the rapid increases in blood flow at the exercise onset are exclusively due to the mechanical effects of the muscle pump was tested in six volunteers during dynamic handgrip exercise. While supine, each subject completed a series of eight different exercise tests in which brachial artery blood pressure (BP) was altered by 25-30 mmHg (1 mmHg = 133.3 Pa) by positioning the arm above or below the heart. Two different weights, corresponding to 4.9 and 9.7% of maximal voluntary isometric contraction, were raised and lowered at two different contraction rate schedules (1s:1s and 2s:2s work-rest) each with a 50% duty cycle. Beat-by-beat measures of mean blood velocity (MBV) (pulsed Doppler) were obtained at rest and for 5 min following step increases in work rate with emphasis on the first 24 s. MBV was increased 50-100% above rest following the first contraction in both arm positions (p < 0.05). The increase in MBV from rest was greater in the below position compared with above, and this effect was observed following the first and subsequent contractions (p < 0.05). However, the positional effect on the increase in MBV could not be explained entirely by the approximately 40% greater BP in this position. Also, the greater workload resulted in greater increases in MBV as early as the first contraction, compared with the light workload (p < 0.05) despite similar reductions in forearm volume following single contractions. MBV was greater with faster contraction rate tests by 8 s of exercise. It was concluded that microvascular vasodilation must act in concert with a reduction in venous pressure to increase forearm blood flow within the initial 2-4 s of exercise.     

Three-dimensional visualization of physiologically based kinetic model outputs

Outputs from a physiologically based toxicokinetic (PB-TK) model for fish were visualized by mapping time-series data for specific tissues onto a three-dimensional representation of a rainbow trout. The trout representation was generated in stepwise fashion: 1) cross-section images were obtained from an anesthetized fish using a magnetic resonance imaging system, 2) images were processed to classify tissue types and eliminate unnecessary detail. 3) processed images were imported to a visualization software package (Application Visualization System) to create a three-dimensional representation of the fish, encapsulating five volumes corresponding to the liver, kidney, muscle, gastrointestinal tract, and fat, Kinetic data for the disposition of pentachloroethane in trout were generated using a PB-TK model. Model outputs were mapped onto corresponding tissues volumes, representing chemical concentration as color intensity. The workstation software was then used to animate the images, illustration the accumulation of pentachloroethane in each tissue during a continuous branchial (gill) exposure.