Snaps of a tiny amphipod push the boundary of ultrafast, repeatable movement.

Surprisingly, the fastest motions are not produced by large animals or robots. Rather, small organisms or structures, including cnidarian stinging cells, fungal shooting spores, and mandible strikes of ants, termites, and spiders, hold the world acceleration records.1-5 These diverse systems share common features: they rapidly convert potential energy - stored in deformed material or fluid - into kinetic energy when a latch is released.4-6 However, the fastest of these are not repeatable, because mechanical components are broken or ejected.5,6 Furthermore, some of these systems must overcome the added challenge of moving in water, where high density and viscosity constrain acceleration at small sizes. Here we report the kinematics of repeatable, ultrafast snaps by tiny marine amphipods (Dulichiella cf. appendiculata). Males use their enlarged major claw, which can exceed 30% of body mass, to snap a 1 mm-long dactyl with a diameter equivalent to a human hair (184 µm). The claw snaps closed extremely rapidly, averaging 93 µs, 17 m s-1, and 2.4 x 105 m s-2. These snaps are among the smallest and fastest of any documented repeatable movement, and are sufficiently fast to operate in the inertial hydrodynamic regime (Reynolds number (Re) >10,000). They generate audible pops and rapid water jets, which occasionally yield cavitation, and may be used for defense. These amphipod snaps push the boundaries of acceleration and size for repeatable movements, particularly in water, and exemplify how new biomechanical insights can arise from unassuming animals. VIDEO ABSTRACT.

Adhesive latching and legless leaping in small, worm-like insect larvae.

Jumping is often achieved using propulsive legs, yet legless leaping has evolved multiple times. We examined the kinematics, energetics and morphology of long-distance jumps produced by the legless larvae of gall midges (Asphondylia sp.). They store elastic energy by forming their body into a loop and pressurizing part of their body to form a transient 'leg'. They prevent movement during elastic loading by placing two regions covered with microstructures against each other, which likely serve as a newly described adhesive latch. Once the latch releases, the transient 'leg' launches the body into the air. Their average takeoff speeds (mean: 0.85 m s-1; range: 0.39-1.27 m s-1) and horizontal travel distances (up to 36 times body length or 121 mm) rival those of legged insect jumpers and their mass-specific power density (mean: 910 W kg-1; range: 150-2420 W kg-1) indicates the use of elastic energy storage to launch the jump. Based on the forces reported for other microscale adhesive structures, the adhesive latching surfaces are sufficient to oppose the loading forces prior to jumping. Energetic comparisons of insect larval crawling versus jumping indicate that these jumps are orders of magnitude more efficient than would be possible if the animals had crawled an equivalent distance. These discoveries integrate three vibrant areas in engineering and biology - soft robotics, small, high-acceleration systems, and adhesive systems - and point toward a rich, and as-yet untapped area of biological diversity of worm-like, small, legless jumpers.

NO modulates norepinephrine release in human skeletal muscle: implications for neural preconditioning.

The purpose of this study was to estimate muscle interstitial norepinephrine (NE) levels during exercise and to determine whether nitric oxide (NO) modulates NE release in the skeletal muscle in humans. We measured interstitial dialysate concentrations of NE with two microdialysis probes inserted into the forearm. Probes were perfused with saline and the NO synthesis inhibitor N(G)-monomethyl-L-arginine (L-NMMA), respectively. Dialysate samples were collected during two sequential 20-min intense dynamic handgrip periods, preceded by 40-min baseline periods. On a different day, forearm ischemia was performed instead of the first exercise period. Exercise increased dialysate NE from 172 +/- 42 to 270 +/- 45 pg/ml (83% increase, P < 0.02, n = 6). Probes perfused with L-NMMA had a 136 +/- 39% greater dialysate NE compared with probes perfused with saline (225 +/- 25 vs. 125 +/- 25 pg/ml, P < 0.001, n = 9). The exercise-induced increase in NE (125 +/- 52%) was attenuated if preceded by exercise (34 +/- 34%) or ischemia (40 +/- 36%; P = 0.06, n = 6), suggesting a neural preconditioning effect. This attenuation was not observed in probes perfused with L-NMMA. We propose that NO modulates NE release in skeletal muscle, that ischemic exercise increases muscle interstitial NE, and that this increase can be attenuated by a preconditioning effect mediated in part by NO.

Adenosine, a metabolic trigger of the exercise pressor reflex in humans.

There is substantial evidence that adenosine activates muscle afferent nerve fibers leading to sympathetic stimulation, but the issue remains controversial. To further test this hypothesis, we used local injections of adenosine into the brachial artery while monitoring systemic muscle sympathetic nerve activity (MSNA) with peroneal microneurography. The increase in MSNA induced by 3 mg intrabrachial adenosine (106+/-32%) was abolished if forearm afferent traffic was interrupted by axillary ganglionic blockade (21+/-19%, n=5, P:<0.05). Furthermore, the increase in MSNA induced by intravenous adenosine was 3.7-fold lower and later (onset latency 20.9+/-4.8 seconds versus 8.5+/-1 seconds) than intrabrachial adenosine. Finally, we used forearm exercise (dynamic handgrip at 50% and 15% maximal voluntary contraction, MVC), with or without superimposed ischemia, to modulate interstitial levels of adenosine (estimated with microdialysis) while monitoring MSNA. Fifteen minutes of intense (50% MVC) and moderate (15% MVC) exercise increased adenosine dialysate concentrations from 0.31+/-0.1 to 1.24+/-0.4 micromol/L (528+/-292%) and from 0.1+/-0.02 to 0.419+/-0.16 micromol/L (303+/-99%), respectively (n=7, P:<0.01). MSNA increased 88+/-25% and 38+/-28%, respectively. Five minutes of moderate exercise increased adenosine from 0.095+/-0.02 to 0.25+/-0.12 micromol/L, and from 0.095+/-0.02 to 0.48+/-0.19 micromol/L when ischemia was superimposed on exercise (n=7, P:=0.01). The percent increase in MSNA induced by the various interventions correlated with the percent increase in dialysate adenosine levels (r=0.96). We conclude that adenosine activates muscle afferent nerves, triggering reflex sympathetic activation.

The role of jelly coats in sperm-egg encounters, fertilization success, and selection on egg size in broadcast spawners.

Sperm limitation may be an important selective force influencing gamete traits such as egg size. The relatively inexpensive extracellular structures surrounding many marine invertebrate eggs might serve to enhance collision rates without the added cost of increasing the egg cell. However, despite decades of research, the effects of extracellular structures on fertilization have not been conclusively documented. Here, using the sea urchin Lytechinus variegatus, we remove jelly coats from eggs, and we quantify sperm collisions to eggs with jelly coats, eggs without jelly coats, and inert plastic beads. We also quantify fertilization success in both egg treatment groups. We find that sperm-egg collision rates increase as a function of sperm concentration and target size and that sperm are not chemotactically attracted to eggs nor to jelly coats in this species. In fertilization assays, the presence of the jelly coat is correlated with a significant but smaller-than-expected improvement in fertilization success. A pair of optimality models predict that, despite the large difference in the energetic value of egg contents and jelly material, the presence of the jelly coat does not diminish selection for larger egg cell size when sperm are limiting.

Neural firing in ventrolateral thalamic nucleus during conditioned vocal behavior in cats.

The ventrolateral (VL) thalamus in mammals is a site well-situated to show vocalization-related neural activity if there is general or classical motor system involvement in vocal production. It receives input from both the basal ganglia and cerebellum, and forms reciprocal connections with motor cortical areas. The current study examined the activity in cat VL thalamus neurons during instrumentally conditioned vocalization. Units in our sample showed irregular spontaneous firing which could be modulated by slowly occurring fluctuations in intensity of vocalization task performance. Two main types of behavioral events were associated with changes in neural firing rate. The first of these was the ingestion of food reward. More than half of all recordings showed phasic bursting patterns during licking; a similar number had increases in firing preparatory to this phasic activity. The second behavioral event modulating unit responses was vocalization. Approximately 60% of recordings showed activity changes time-locked to vocalization. These responses were almost always excitatory, and often involved changes in firing that preceded vocalization onset. No spatial organization of differences in firing pattern between neurons could be distinguished. Our results suggest that VL thalamus may well be involved in mediating vocal behavior, although its functional role remains an object of speculation. Results are compared with previous studies of vocalization-related activity and of VL thalamus activity.

A biomechanical laryngeal model of voice F0 and glottal width control.

A simplified mathematical model of the larynx, based on biomechanical principles, is described. Components represented include cartilages (cricoid, thyroid, arytenoids, and corniculates), muscles (thyroarytenoid [TA], cricothyroid pars rectus [CTR], cricothyroid pars oblique [CTO], posterior cricoarytenoid [PCA], lateral cricoarytenoid [LCA], and transverse arytenoid [TrA]), ligaments (cricoarytenoid [CAL], anterior cricothyroid [ACTL], posterior cricothyroid [PCTL], and vocal ligaments [VL]), and subglottal pressure (PS). Model outputs included equilibrium positions of cartilages, the glottal width, and the estimated fundamental frequency (F0) of vocal fold vibration. Major findings were that TA, CTR, CTO, and TrA all had substantial effects on F0: that PCA caused glottal opening by rotating the arytenoids laterally; that LCA both ventrolaterally translated and medially rotated the arytenoids, producing minimal effects on glottal closure; and that TrA had major effects on glottal closure by dorsomedially translating and medially rotating the arytenoids. The effects of LCA and PCA were generally diminished as activation of other muscles was increased. Muscle activation plots (MAPs) were used to study the effects of independent parametric variation of several muscles on F0 and glottal width. Both of these parameters were found to be under simultaneous control by TA, CTR, CTO, and TrA. LCA and PCA also had some influence on F0 and glottal width contours, but this appeared to be of limited functional significance, since changes in F0 tended to be offset by changes in glottal closure. Finally, the functional significance of rotation and subduction of the cricothyroid joint was examined. It was found that the combination of subduction with rotation provided greatest control and range of Fo as muscle activation was varied systematically. Strengths and limitations of the current model are discussed, future developments are suggested, and implications of model results as constraints for neural modeling efforts are described.

Intellectual competence of children who are beginning inpatient and day psychiatric treatment.

Intellectual abilities of 300 children with serious emotional disorders, referred to either psychiatric day- or inpatient-hospital treatment, were compared. Comparisons also were made to WISC-R standardization data. The findings indicated that children referred to inpatient settings were similar in intellectual competency to children in day treatment. Also, children with serious emotional disorders did not appear to differ strongly in clinically meaningful ways from the WISC-R standardization sample, a finding that replicates results of other investigators. Three distinct, clinically useful profiles emerged from a cluster analysis of the total group that may be practical in planning educational and therapeutic interventions in treatment settings for seriously disturbed children. The profiles underscored the wide range of intellectual abilities represented among these children.

Control of voice F0 by an artificial neural network.

An artificial neural network model is presented which might correspond to one component of fundamental frequency (F0) control by the brain. Good F0 control could be achieved using only seven neurodes. These included three motor neurodes, a single inhibitory neurode influencing only the thyroarytenoid (TA) motor neurode, and three excitatory neurodes, one of which excited all motor neurodes and two of which excited the inhibitory neurode. The potential utility of this type of model in the study of mechanisms of vocal control is discussed.

Incarcerated hernia with intestinal obstruction after laparoscopic cholecystectomy.

Use of laparoscopic surgical procedures have expanded in the past several years, but physicians must be cognizant of the potential complications. One such complication, intestinal obstruction, is discussed, as is the importance of CT scan in making a definitive diagnosis.

Comparisons of intellectual performance among children with psychiatric disorders.

The intellectual performances of children with a variety of psychiatric disorders were examined and compared with the findings from a similar study by Hodges and Plow (1990). Mean IQ scores were in the average range for both study samples, and no significant differences were found in WISC-R summary scores. Nevertheless, the Hodges and Plow findings were only partially corroborated. They observed, for instance, a relative deficit in verbal abilities for conduct-disordered children and lower IQ scores for children with anxiety disorders vs. children with all other disorders. Our replication study found no significant differences among the disorder groups for any of the scores examined. Possible explanations for the divergence in findings are discussed.

A quantitative model of voice F0 control.

A mathematical model of the larynx, based on biomechanical principles, is described. Components represented include two cartilage elements (cricoid with locked arytenoids, and thyroid), three muscles (thyroarytenoid [TA], cricothyroid pars rectus [CTr], and cricothyroid pars oblique [CTo]), and two ligaments (cricothyroid and vocal ligaments), as well as subglottal pressure (PS). For any combination of muscle activities and PS level, equilibrium positions and tensions could be calculated for components in the system. The tensions and lengths of vocal fold elements were then used to calculate fundamental frequency (F0) of vocal fold vibration. Systematic variation of model muscle activation and PS patterns allowed study of the behavior of the model. TA activity tended to shorten the vocal folds; increased levels of CTr and CTo activity, and PS, had the opposite effect. Increased activity of any muscle tended to increase vocal fold tension, while PS increases were mainly ineffective. F0 was generally increased by increased CTr, CTo, and PS values. However, TA activity had a strongly nonmonotonic effect on F0. Best control of F0 could be achieved only by a process of co-contraction of all muscles at low frequencies, followed by sustained contraction of CTr and CTo with decreasing TA activity for F0's increasing above this low-frequency range. These results are discussed in terms of their possible implications for norma and abnormal voice production, and as a set of constraints for neural modeling efforts.

Home behaviors of children in three treatment settings: an outpatient clinic, a day hospital, and an inpatient hospital.

OBJECTIVE: To compare parents' ratings of home behaviors of three groups of children: those entering an outpatient clinic, a day hospital, and an inpatient hospital. It was hypothesized that the home behaviors of children starting day and inpatient hospital treatment would be rated as significantly more deviant than those of children beginning outpatient treatment, and there would be no significant differences in behavior ratings of children beginning day and inpatient hospital treatment. METHOD: A standardized behavior checklist was completed by the primary parent at the time treatment was begun. Scores on four factor scales were obtained, and a multivariate analysis of covariance was carried out. RESULTS: The hypotheses were partially supported. Children beginning day and inpatient hospitalization were seen as more disordered, anxious, and aggressive than were those starting outpatient treatment; children starting day treatment were reported as more learning disabled than were those in both outpatient and inpatient settings; and children entering the inpatient setting were perceived as more aggressive than were those in day treatment. CONCLUSION: Aggressive behavior and learning disability appear to be determinants of choice of treatment setting. The progression from least to most restrictive placement was demonstrated for aggressive behavior only.

The school behaviors of children in three psychiatric treatment settings: an outpatient clinic, a day hospital, and an inpatient hospital.

Compares teachers' ratings of the school behaviors of children entering an outpatient clinic, a day psychiatric program, and an inpatient psychiatric hospital. Many of the ratings did not discriminate among the three groups. Children starting outpatient versus day treatment were rated as higher in aggression, anxiety, and hostile withdrawal, and children beginning outpatient and day treatment versus inpatient treatment, were reported as more skilled socially.

Academic achievement of children with emotional disorders treated in a day hospital program: an outcome study.

Reading, spelling, and arithmetic achievement of children treated in a day psychiatric hospital was examined over time. The results indicated that the majority of children fell in the average and above achievement group and progressed evenly over time. Almost none got worse and only a few made large gains. Organic impairment ratings appeared to distinguish the three performance groups within each subject area.

Vocalizations in the cat: behavioral methodology and spectrographic analysis.

Attempts to understand the neural mechanisms underlying mammalian vocal behaviors, including speech, require study of the neural activity and anatomy of vocalization-controlling brain structures. Such studies necessitate the application of invasive neurobiological techniques in animal models. In the current study, cats are used in the development of an animal model of vocal tract control. The animals are instrumentally conditioned to vocalize for food reward. Acquisition of this task can occur within a few minutes, although additional training generally is required to solidly establish the behavior and to train subjects to produce consistently high rates of vocalization for prolonged periods of time. Following training, animals can generally sustain a rate of two calls per minute for a period of over two hours. Optimal task performance is partly dependent on motivation level. Although there is considerable variation between animals, the vocalizations produced have an average duration of 600 ms and a fundamental frequency of around 500 Hz. In addition, during a typical vocalization, there are dynamic variations of about 150 Hz for fundamental frequency and 17 dB for sound intensity. These variations provide opportunities for relating neural and muscular activity to different aspects of the vocal behavior they control. Based on a number of considerations, the model and techniques discussed here probably are most applicable to studying the neurobiology of sub-cortical nuclei subserving vocal control. Similar mechanisms might well be present in other species, including humans. Thus, data obtained from study of this model may be applicable to understanding the processes underlying vocal tract control during human speech.

Factors influencing neural activity in parabrachial regions during cat vocalizations.

The parabrachial nucleus in mammals is intimately connected with other vocalization controlling brainstem structures. It, along with ventromedially adjacent structures, also has been identified as the pneumotaxic center, and as such shows strong respiratory related activity in the anesthetized cat. The current study examines the neuronal activity in cat parabrachial regions during production of instrumentally conditioned vocalizations. Most of the units in our sample show considerable activity during periods between vocalizations. For many units, firing rate fluctuates during the respiratory cycle, although apparently not as strongly as reported in the decerebrate cat. Also, there is often strong phasic activity during periods where animals are licking to ingest their food rewards. During the peri-vocalization period, various neural activity patterns can be recorded. Most common is an activity increase during the vocalization itself. Moreover, in some units, this activity increase has an auditory component. A smaller number of units show other activity patterns, including a suppression of activity during vocalization and activity increases preceding the vocalization. Overall, our results suggest that the parabrachial region's involvement in vocal control is quite complex, involving convergence of respiratory, acoustic, vocalization-related, and perhaps somatosensory influences.

Coding of spectral fine structure in the auditory nerve. II: Level-dependent nonlinear responses.

Phase-locked discharge patterns of single cat auditory-nerve fibers were analyzed in response to complex tones centered at fiber characteristic frequency (CF). Signals were octave-bandwidth harmonic complexes defined by a center frequency F and an intercomponent spacing factor N, such that F/N was the fundamental frequency. Parameters that were manipulated included the phase spectrum, the number of components, and the intensity of the center component. Analyses employed Fourier transforms of period histograms to assess the degree to which responses were synchronized to the frequencies present in the acoustic stimulus. Several nonlinearities were observed in the response as intensity was varied between threshold and 80-90 dB SPL. Response nonlinearities were strong for all signals except those with random phase spectra. The most commonly observed nonlinearity was an emphasis of one or more stimulus components in the response. The degree of nonlinearity usually increased with intensity and signal complexity and decreased with fiber frequency selectivity. Half-wave rectification introduced synchronization to the missing fundamental. The strength of the response at the fundamental was related to stimulus crest factor. Signals with low center frequencies and high crest factors often elicited instantaneous discharge rates at the theoretical maximum of pi CF. This suggests that the probability of spike generation approaches one during high-amplitude waveform segments. Response nonlinearity was interpreted as arising from three sources, namely, cochlear mechanics, compression of instantaneous discharge rate, and saturation of average discharge rate. At near-threshold intensities, fibers with high spontaneous rates exhibited responses that were linear functions of stimulus waveshape, whereas fibers with low spontaneous spike rates produced responses that were best described in terms of an expansive nonlinearity.