Analysis of expressed sequence tags from Uromyces appendiculatus hyphae and haustoria and their comparison to sequences from other rust fungi.

Hyphae, 2 to 8 days postinoculation (dpi), and haustoria, 5 dpi, were isolated from Uromyces appendiculatus infected bean leaves (Phaseolus vulgaris cv. Pinto 111) and a separate cDNA library prepared for each fungal preparation. Approximately 10,000 hyphae and 2,700 haustoria clones were sequenced from both the 5' and 3' ends. Assembly of all of the fungal sequences yielded 3,359 contigs and 927 singletons. The U. appendiculatus sequences were compared with sequence data for other rust fungi, Phakopsora pachyrhizi, Uromyces fabae, and Puccinia graminis. The U. appendiculatus haustoria library included a large number of genes with unknown cellular function; however, summation of sequences of known cellular function suggested that haustoria at 5 dpi had fewer transcripts linked to protein synthesis in favor of energy metabolism and nutrient uptake. In addition, open reading frames in the U. appendiculatus data set with an N-terminal signal peptide were identified and compared with other proteins putatively secreted from rust fungi. In this regard, a small family of putatively secreted RTP1-like proteins was identified in U. appendiculatus and P. graminis.

Dynamic myocardial contractile parameters from left ventricular pressure-volume measurements.

A new dynamic model of left ventricular (LV) pressure-volume relationships in beating heart was developed by mathematically linking chamber pressure-volume dynamics with cardiac muscle force-length dynamics. The dynamic LV model accounted for >80% of the measured variation in pressure caused by small-amplitude volume perturbation in an otherwise isovolumically beating, isolated rat heart. The dynamic LV model produced good fits to pressure responses to volume perturbations, but there existed some systematic features in the residual errors of the fits. The issue was whether these residual errors would be damaging to an application where the dynamic LV model was used with LV pressure and volume measurements to estimate myocardial contractile parameters. Good agreement among myocardial parameters responsible for response magnitude was found between those derived by geometric transformations of parameters of the dynamic LV model estimated in beating heart and those found by direct measurement in constantly activated, isolated muscle fibers. Good agreement was also found among myocardial kinetic parameters estimated in each of the two preparations. Thus the small systematic residual errors from fitting the LV model to the dynamic pressure-volume measurements do not interfere with use of the dynamic LV model to estimate contractile parameters of myocardium. Dynamic contractile behavior of cardiac muscle can now be obtained from a beating heart by judicious application of the dynamic LV model to information-rich pressure and volume signals. This provides for the first time a bridge between the dynamics of cardiac muscle function and the dynamics of heart function and allows a beating heart to be used in studies where the relevance of myofilament contractile behavior to cardiovascular system function may be investigated.

Comparative analysis of aortic impedance and wave reflection in ferrets and dogs.

Our modified version of the T-tube arterial model (consisting of two parallel, loss-free transmission paths terminating in lumped loads of complex and frequency-dependent nature) was applied to experimental measurements of ascending aortic pressure and of ascending and descending aortic flows taken from dogs and ferrets. Our aim was to provide quantitative evaluation of the aortic pressure and flow pulse wave components as they relate to the distribution of arterial properties and relate to wave travel and reflection in mammalians of consistently different size and shape. Estimated effective lengths (distances to effective reflection sites) of the head-end (d(h)) and body-end (d(b)) transmission paths were approximately 12 and 30 cm, respectively, in the dog and 6.5 and 13 cm, respectively, in the ferret. These lengths and distributions of estimated arterial properties were consistent with the difference in the body size and with the more central location of the heart in the ferret's body than it is in the dog's body. In both animal species the ascending aortic pressure and flow waves could be interpreted in terms of forward and reflected components arising from the two distinct effective reflection sites, although the higher d(h)/d(b) ratio in the ferret determined the presence of one broad, indistinct minimum in the modulus of ascending aortic impedance in the frequency range from 0 to 10 Hz, rather than two distinct minima as observed in the dog.

Neurophysiological evidence for the detection of external stimuli during sleep.

STUDY OBJECTIVES: A cognitive evoked potential, labelled "P300," is elicited when an observer attends to and detects an infrequently delivered "target" stimulus. It is not typically present if the target is ignored or undetected. P300 is therefore thought to reflect some aspect of consciousness of the stimulus. There has been much controversy concerning whether P300 can be recorded in sleep, a state in which information processing of external events is presumably reduced. The present study investigated the effects of both pitch and intensity stimuli on information processing, in order to determine whether a more salient stimulus might elicit a P300 in sleep that is comparable to the waking P300. DESIGN: A true P300 will have a parietal maximum peak following a rare stimulus, and its amplitude will vary inversely with the probability of stimulus delivery. Participants were thus randomly assigned to one of three probability groups, in which the deviant was presented on 20%, 10%, or 5% of trials. SETTING: Data were collected in the Human Neurophysiology Laboratory at the University of Ottawa. PARTICIPANTS: Twenty-four young adults. INTERVENTIONS: N/A. MEASUREMENTS AND RESULTS: During wakefulness, a parietal P300 was apparent following both pitch and intensity deviants when participants were asked to detect deviant stimuli. A P300 was also apparent following the intensity deviant when participants were instructed to ignore the stimuli. During non-REM sleep, no P300 could be identified. In REM sleep, very rare (p=.05) loud deviants elicited a parietal P300. This P300 was attenuated relative to the waking ignore condition. Moreover, the frontal dispersion of the peak was absent. CONCLUSIONS: These data provide evidence that participants are conscious (parietal P300) of very rare and intrusive stimuli during REM sleep, although the frontal aspects associated with this consciousness may be absent.

Nonlinear myofilament regulatory processes affect frequency-dependent muscle fiber stiffness.

To investigate the role of nonlinear myofilament regulatory processes in sarcomeric mechanodynamics, a model of myofilament kinetic processes, including thin filament on-off kinetics and crossbridge cycling kinetics with interactions within and between kinetic processes, was built to predict sarcomeric stiffness dynamics. Linear decomposition of this highly nonlinear model resulted in the identification of distinct contributions by kinetics of recruitment and by kinetics of distortion to the complex stiffness of the sarcomere. Further, it was established that nonlinear kinetic processes, such as those associated with cooperative neighbor interactions or length-dependent crossbridge attachment, contributed unique features to the stiffness spectrum through their effect on recruitment. Myofilament model-derived sarcomeric stiffness reproduces experimentally measured sarcomeric stiffness with remarkable fidelity. Consequently, characteristic features of the experimentally determined stiffness spectrum become interpretable in terms of the underlying contractile mechanisms that are responsible for specific dynamic behaviors.

Effects of sequential and temporal probability of deviant occurrence on mismatch negativity.

The mismatch negativity (MMN) increases in amplitude as the probability of deviant occurrence decreases. It is unclear whether the determining variable is sequential probability (i.e. the probability of a deviant within a number of standards) or temporal probability (i.e. the probability of a deviant within a period of time). Eight subjects heard a train of frequently occurring 1000 Hz standard tones. The probability of a 1100 Hz pitch deviant was manipulated. In one condition the stimulus-onset-asynchrony (SOA) was 150 ms, with temporal probability of deviant occurrence being either 1/9.00, 1/4.50, 1/2.25, or 1/1.125 s (sequential probability being 1/60, 1/30, 1/15, or 1(deviant)/7.5(standards), respectively). In another condition the SOA was 600 ms, with temporal probability being either 1/9.00, 1/4.50, or 1/2.25 s (sequential probability being 1/15, 1/7.5, or 1/3.75, respectively). In a final condition, the SOA was 2400 ms with temporal probability being 1/9.00 s (sequential probability 1/3.75). Both sequential and temporal probabilities had a marked effect on the MMN. When a deviant occurred every 2.25, 4.50, or 9.00 s, the MMN increased as temporal probability decreased. When a deviant occurred once every 7.5 or 15 standards, the MMN was larger for lower sequential probability, but the effect was not significant. Nevertheless, when temporal probability was held constant at 1/9.00 s, the MMN increased as sequential probability decreased. At rapid rates of stimulus presentation, the MMN was largest. However, it was attenuated when the probability of deviant occurrence was very high perhaps due to the refractoriness of its generator. At the slowest rate, the MMN was diminished perhaps due to memory decay for the standard stimuli.

Myofilament kinetics in isometric twitch dynamics.

To better understand the relationship between kinetic processes of contraction and the dynamic features of an isometric twitch, studies were conducted using a mathematical model that included: (1) kinetics of cross bridge (XB) cycling; (2) kinetics of thin filament regulatory processes; (3) serial and feedback interactions between these two kinetic processes; and (4) time course of calcium activation. Isometric twitch wave forms were predicted, morphometric features of the predicted twitch wave form were evaluated, and sensitivities of wave form morphometric features to model kinetic parameters were assessed. Initially, the impulse response of the XB cycle alone was analyzed with the findings that dynamic constants of the twitch transient were much faster than turnover number of steady-state XB cycling, and, although speed and duration of the twitch wave form were sensitive to XB cycle kinetic constants. parameters of wave shape were not. When thin filament regulatory unit (RU) kinetics were added to XB cycle kinetics, the system impulse response was slowed with only little effect on wave shape. When cooperative neighbor interactions between RU and XB were added, twitch wave shape (as well as amplitude, speed and duration) proved to be sensitive to variation in cooperativity. Importantly, persistence and shape of the falling phase could be strongly modified. When kinetic coefficients of XB attachment were made to depend on sarcomere length, changes in wave shape occurred that did not occur when only sliding filament mechanisms were operative. Indeed, the force-length relationship proved to be highly sensitive to length-dependent XB attachment in combination with cooperative interactions. These model findings are the basis of hypotheses for the role of specific kinetic events of contraction in generating twitch wave form features.

The intensity of masking noise affects the mismatch negativity to speech sounds in human subjects.

The present study investigated the effects of decreased audibility of the speech sounds 'ba' and 'da' on the mismatch negativity (MMN). Audibility was altered by varying the intensity of the masking noise to be either 0 (no noise), 65, 70 or 75 dB speech perception level. Cortical event-related potentials were recorded while normal listeners (n=7) were instructed to ignore the stimuli. In a separate condition, subjects were asked to signal detection of the deviant stimulus by button-press. As audibility of speech sounds was decreased, MMN peak amplitude decreased and MMN peak latency increased. Behavioral responses were in accordance with the MMN data. Hit rates decreased as audibility decreased. These results suggest that both pre-attentive and attentive speech discrimination deteriorate following a reduction in audibility.

Effects of attention and semantic relation on event-related potentials in a picture-word naming task.

The interactive effects of attention and semantic relation on event-related potential (ERP) waveforms were examined during a naming task in which the physical stimulus array was the same across conditions. Superimposed picture-word pairs were presented in which the meaning of the words and pictures was congruent, semantically associated, or incongruent. In separate conditions, participants named words or pictures while ignoring the other stimulus. When words were attended, the superimposed pictures modulated the amplitude of P240 waves at posterior sites compared with when words were presented individually, but had no effect on N450 waves. In contrast, when pictures were attended to, the superimposed incongruent words elicited larger amplitude N450 waves at anterior sites than did congruent words or individually presented pictures. These effects affirm the independent processing of words and pictures during attention and are consistent with automatic and controlled processing of words and pictures, respectively. They also illustrate the endogenous nature of these late ERP waves.

Multiple P3 evidence of a two-stage process in word gender decision.

All French nouns must be assigned to one of two grammatical genders: masculine or feminine. Participants used either the superordinate labels masculin/féminin or the singular indefinite articles un/une to classify French target nouns. Reaction time to the labels masculin/féminin was about 200 ms longer than to the un/une labels. When the indefinite articles were used, a single P3 peak of the event-related potential was elicited. When superordinate labels were used, a double-peaked positivity was observed. The latency of the initial P3 in the masculin/féminin trials was not significantly different from that in the un/une trials. The second positive wave peaked approximately 300 ms following the first. An explanation consistent with these data is that subjects used a two-stage process to classify the nouns appearing with superordinate labels.

Individual differences in mismatch negativity measures of involuntary attention shift.

OBJECTIVE: The purpose of this study was to compare the automatic detection of deviance in introverts and extraverts. Event-related potentials were recorded to standard and deviant stimuli. These were presented either rapidly or slowly. Stimuli that are presented slowly may intrude into consciousness. METHODS: Twenty subjects were tested and divided into introverted and extraverted groups. A 500 Hz standard stimulus was presented on 85% of trials. On the remaining 15% of trials, a 750 Hz deviant was presented. In separate conditions, stimuli were presented rapidly (every 500 ms) or slowly (every 1500 ms). Subjects ignored the stimuli while reading. RESULTS: The deviant stimulus elicited a mismatch negativity (MMN) in both conditions. No inter-group differences in the MMN emerged when a rapid rate of presentation was employed. When a slower rate was employed, a late negativity was significantly larger for the extraverted than the introverted group. This was followed by a late positive wave. CONCLUSION: The late negative-positive complex is thought to reflect intrusiveness. It would therefore appear that extraverts are more distractible than introverts when stimuli are presented slowly.

Physiological relevance of uniform elastic tube-models to infer descending aortic wave reflection: a problem of identifiability.

A uniform, frictional elastic tube terminating in a pure resistor (model A), was compared with a uniform, frictionless elastic tube, terminating in a first-order low-pass filter load (model B). The aim was to address an identifiability problem in uniqueness of parameter estimates and to evaluate the physiological meaning of tube-length estimates obtained from these models applied to the descending aortic circulation. Measurements of high descending aortic pressure and flow were taken from three anaesthetized, open-chest dogs and used to estimate the model parameters. A simultaneous measurement of terminal aortic pressure was used to estimate the foot-to-foot pulse wave velocity. A flow-fitting procedure yielded a multiplicity of equivalent solutions for the wave transit time across the transmission tubes (tau(ai), for model A and tau(bi) for model B, i=0,1,2,...,N,...) and the related tube-lengths d(ai) and d(bi), respectively. The tube length represents the distance to an effective reflection site (effective length) of the descending aortic circulation. Assuming that this length should be no longer than the dimensions of the body, the lowest estimates (i=0) of wave transit time and tube length (average +/- SE: tau(ao)=85.7+/-10.8 ms and d(ao)=53.4+/-3.7 cm for model A; tau(bo)=46.6+/-6.7 ms and d(bo)= 29.1+/-3.5 cm for model B) were identifiable as unique and acceptable solutions. Model A located the effective reflection site a few centimeters below the terminal aortic region. This location is inconsistent with the use of a pure resistor as a tube's terminal load. Further, relatively high estimates of longitudinal frictional losses violated the assumption of small losses across the transmission path and yielded an unphysiological mean-pressure drop of 7.1+/-2.3 mmHg. The estimates of d(bo) provided by model B located the effective reflection site near the origin of the renal arteries. The model-predicted pressure wave at this location approximated the measured pressure. Thus, model B represents a significant improvement over model A as a tool to infer wave travel and reflection in the descending aortic circulation.

Overall cardiac functional effect of positive inotropic drugs with differing effects on relaxation.

Recent interest in so-called calcium-sensitizing positive inotropic drugs has highlighted the potential problem of a positive effect on force development being offset, at least partially, by the negative effect that many of these drugs have on relaxation. The purpose of this study was to examine the interplay of contraction and relaxation in determining the overall cardiac effect of different positive inotropic drugs. Using a buffer-perfused isolated rabbit heart preparation, we studied four drugs (calcium, dobutamine, EMD 57033, and CGP 48506) that were given at doses sufficient to increase similarly left ventricular pressure-generating capability by approximately 20%. We show that, even though they produce equivalent changes in pressure-generating capability, these four agents produce dissimilar changes in relaxation capability, with dobutamine speeding relaxation, EMD 57033 slowing relaxation, and calcium and CGP 48506 having little effect of relaxation. Similar relative effects were observed for drug-induced changes in the timing of pressure-generation events. These effects combine to produce different drug-induced changes in overall cardiac pump function judged by the relation between cardiac output and heart rate. Dobutamine shifted the maximal cardiac output to a higher heart rate. In contrast, both calcium sensitizers shifted the maximum in cardiac output to a lower heart rate, whereas calcium had no effect. Thus even though positive inotropic drugs may have similar effects on left ventricular pressure generation, the overall benefit of such drugs on ventricular pump function will depend on how the drug also affects ventricular relaxation and ejection capabilities.

Mismatch negativity to inclusions and omissions of stimulus features.

Two experiments were run to determine the effects of addition or removal of a stimulus feature on mismatch negativity (MMN). In the first experiment, a deviant stimulus was constructed by adding a click to a white noise standard stimulus. In the second experiment, the deviant was constructed by subtracting the click from the standard. In different conditions, the intensity of the click was varied. When the deviant was constructed by the addition of a click, a significant MMN was evident in those conditions in which click-to-noise ratio exceeded 1.0. When the deviant was constructed by the subtraction of the click, a significant negativity was found only when the click-to-noise ratio was very large. However, this negativity was accompanied by only a small polarity inversion at the mastoid. The MMN is thus best elicited when the deviant stimulus contains a new afferent element not present in the standard stimulus.

Different myofilament nearest-neighbor interactions have distinctive effects on contractile behavior.

Cooperativity in contractile behavior of myofilament systems almost assuredly arises because of interactions between neighboring sites. These interactions may be of different kinds. Tropomyosin thin-filament regulatory units may have neighbors in steric blocking positions (off) or steric permissive positions (on). The position of these neighbors influence the tendency for the regulatory unit to assume the on or off state. Likewise, the tendency of a myosin cross-bridge to achieve a force-bearing state may be influenced by whether neighboring cross-bridges are in force-bearing states. Also, a cross-bridge in the force-bearing state may influence the tendency of a regulatory unit to enter the on state. We used a mathematical model to examine the influence of each of these three kinds of neighbor interactions on the steady-state force-pCa relation and on the dynamic force redevelopment process. Each neighbor interaction was unique in its effects on maximal Ca(2+)-activated force, position, and symmetry of the force-pCa curve and on the Hill coefficient. Also, each neighbor interaction had a distinctive effect on the time course of force development as assessed by its rate coefficient, k(dev). These diverse effects suggest that variations in all three kinds of nearest-neighbor interactions may be responsible for a wide variety of currently unexplained observations of myofilament contractile behavior.

The mismatch negativity during natural sleep: intensity deviants.

Auditory event-related potentials (ERPs) were recorded from 7 subjects who slept for a single night in the laboratory. An 'oddball' sequence of brief tone pips, differing in intensity, was used. Frequently occurring 70 dB 'standards' were presented with infrequent 80 dB intensity increment deviants and 60 dB intensity decrement deviants. The probability of each deviant was 0.1. Stimuli were presented in a random sequence every 600 ms while subjects were awake but inattentive and during stages 2 and REM of sleep. During wakefulness, the intensity increments elicited a broad fronto-central negativity with two discernable peaks. The first, peaking at approximately 120 ms, showed a polarity inversion at the mastoid and likely represented a summation of the N1 wave and the mismatch negativity (MMN). The second, peaking at approximately 330 ms, may have reflected an enhanced N2b component. In REM sleep, the increment deviants elicited a small amplitude 100-200 ms negativity but its amplitude was not significantly larger than the baseline level. It was followed by a larger and significant 300-450 ms negativity but this was considered too delayed to represent the MMN. The decrement deviants elicited a small amplitude, but statistically non-significant, MMN-like wave during both wakefulness and in REM sleep. A MMN-like wave was absent in stage 2 sleep.

The roles of vertex sharp waves and K-complexes in the generation of N300 in auditory and respiratory-related evoked potentials during early stage 2 NREM sleep.

STUDY OBJECTIVES: To determine the scalp topography of the N300 response to stimuli of different modalities and to investigate the relationship of the N300 component to K-complexes and vertex sharp waves seen in the un-averaged EEG. DESIGN: Two experiments were conducted one using auditory; the other using respiratory occlusion stimuli presented during stage 2 sleep. Trials were classified on the basis of whether they produced a K-complex, a vertex sharp wave, or some other response. Auditory stimuli were presented in the form of an oddball paradigm, and averaged separately depending on whether they were "frequent" or "rare". In both experiments, responses were averaged separately based on the appearance of K-complexes, vertex sharps waves, or some "other" response to the stimuli. SETTING: Data were collected in the Melbourne University Sleep Laboratory. PARTICIPANTS: Young healthy male adults, eight in experiment 1 and six in experiment 2. INTERVENTIONS: NA. MEASUREMENTS AND RESULTS: Data were collected from 29 scalp sites. In all cases, N300 amplitude was maximal in the vertex sharp wave averages, despite being clearly present in the averages of K-complexes and "other" responses. The vertex maximal scalp topography of the N300 did not differ across response conditions or as a function of stimulus modality. This is consistent with the N300 being produced by the same intracranial generators in all cases. There were no effects of stimulus or response type on N300 latency. CONCLUSIONS: N300 should be viewed as a multi-modal component with a different underlying generator mechanism than that of the K-complex.

The role of the spindle in human information processing of high-intensity stimuli during sleep.

Sleep spindles are 12-14 Hz oscillations in EEG, which are thought to inhibit or 'gate' information processing. Event-related potentials may be employed to probe the extent of information processing during sleep. Previous research indicates that event-related potentials elicited by moderate intensity stimuli show increased positivity (or further removal of negativity) when stimuli are presented concurrent with spindles. However, the effectiveness of spindles to inhibit the processing of much louder stimuli remains unknown. The purpose of the present study was to investigate the extent of this gating, by using a range of stimuli including those that are loud and intrusive. Eight good sleepers were recorded during a single night. Auditory stimuli were delivered randomly at 0, 60, 80 or 100 dB SPL. Trials were sorted off-line by sleep stage, stimulus intensity and spindle characteristic (i.e. spindle absent, spindle present). During the sleep-onset period, the often-reported changes in event-related potentials were observed - N1 decreased and P2 increased in amplitude. In Stage 2 sleep, P2 was affected by the presence of spindles, particularly when stimulus intensity was loud. Its amplitude was greatest when spindles occurred following the onset of the stimulus. Scalp-recorded spindles might, therefore, be a consequence of the prior thalamic inhibition of information processing, especially when confronted by loud, intrusive external stimuli.

Secophalloidin and phalloidin-(S)-sulfoxide as contraction modifiers for comparative study of skeletal and cardiac muscles.

Phalloidin, a toxic product of the mushroom Amanita phalloides, binds specifically to F-actin resulting in strong stabilization of F-actin structure (for review, see; Wieland, 1986). Binding to a specific site on the muscle thin filament F-actin, phalloidin modifies contraction in a tissue specific manner. Phalloidin induced changes depend on functionally important parameters (thin filament activation, cross-bridge kinetics), indicating changes in essential steps of the contractile mechanism. Moreover, there is a different action with different phalloidin derivatives. Such properties make phallotoxins (phalloidin and its derivatives) powerful modifiers for muscle research (for review, see: Bukatina, 1996). Phalloidin-induced changes vary qualitatively with muscle types. In all types of skinned skeletal muscle preparations that have been studied (fast and slow muscles from evolutionarily distant animals), the most general effect of phalloidin is to cause a decrease in tension (Bukatina, Morozov, 1979; Alievskaya et al., 1987; Bukatina et al., 1993). In mammalian skeletal muscles, this decrease in tension may be followed by a slowly developing increase in tension. The resulting tension may considerably exceed the tension before phalloidin administration. In contrast, skinned cardiac muscle responds to phalloidin only by increasing isometric tension from the onset of the response. Moreover, the phalloidin response is completed in approximately one-tenth the time in cardiac muscle that it takes in skeletal muscle. These phalloidin effects in cardiac muscle result in an enhanced Ca2+ responsiveness (Boels, Pfitzer, 1992) with an increase in both the force at maximum Ca2+ activation and the Ca2+ sensitivity (Bukatina et al., 1995).

Information processing during sleep onset and sleep.

This Special Section examines the extent of information processing during sleep onset and sleep itself. It is generally agreed that, stimulus input is markedly inhibited during sleep, thus preventing conscious awareness of the external environment. Overt behavioural responses are rarely made within sleep. Two neurophysiological measures are therefore often used. The electrical activity of the brain (the EEG) can be employed to distinguish waking (conscious) from sleeping (unconscious) states. It is also possible to quantify the EEG prior to and following a detection (or a failure of a detection) of a stimulus. Such measures can thus be used to predict conscious awareness. A second measure that frequently has been employed is the brain's response to an external stimulus (the evoked potential). Different components of the evoked potential can be used to trace the extent of information processing during the different states of consciousness. Some are associated with a preconscious detection while others are associated with conscious awareness. Other evoked potentials may be unique to sleep.