Aerobic and anaerobic movement energetics of hybrid and pure parental abalone.

The underlying mechanisms controlling growth heterosis in marine invertebrates remain poorly understood. We used pure blacklip (Haliotis rubra) and greenlip (Haliotis laevigata) abalone, as well as their hybrid, to test whether differences in movement and/or aerobic versus anaerobic energy use are linked to a purported increased growth rate in hybrids. Abalone were acclimated to control (16 °C) and typical summer temperatures (23 °C), each with oxygen treatments of 100% air saturation (O2sat) or 70% O2sat. The experiment then consisted of two phases. During the first phase (chronic exposure), movement and oxygen consumption rates (MO2) of abalone were measured during a 2 day observation period at stable acclimation conditions. Additionaly, lactate dehydrogenase (LDH) and tauropine dehydrogenase (TDH) activities were measured. During phase two (acute exposure), O2sat was raised to 100% for abalone acclimated to 70% O2sat followed by an acute decrease in oxygen to anoxia for all acclimation groups during which movement and MO2 were determined again. During the chronic exposure, hybrids and H. laevigata moved shorter distances than H. rubra. Resting MO2, LDH and TDH activities, however, were similar between abalone types but were increased at 23 °C compared to 16 °C. During the acute exposure, the initial increase to 100% O2sat for individuals acclimated to 70% O2sat resulted in increased movement compared to individuals acclimated to 100% O2sat for hybrids and H. rubra when compared within type of abalone. Similarly, MO2 during spontaneous activity of all three types of abalone previously subjected to 70% O2sat increased above those at 100% O2sat. When oxygen levels had dropped below the critical oxygen level (Pcrit), movement in hybrids and H. laevigata increased up to 6.5-fold compared to movement above Pcrit. Differences in movement and energy use between hybrids and pure species were not marked enough to support the hypothesis that the purportedly higher growth in hybrids is due to an energetic advantage over pure species.

Top-down modulation of auditory processing: effects of sound context, musical expertise and attentional focus.

By recording auditory electrical brain potentials, we investigated whether the basic sound parameters (frequency, duration and intensity) are differentially encoded among speech vs. music sounds by musicians and non-musicians during different attentional demands. To this end, a pseudoword and an instrumental sound of comparable frequency and duration were presented. The accuracy of neural discrimination was tested by manipulations of frequency, duration and intensity. Additionally, the subjects' attentional focus was manipulated by instructions to ignore the sounds while watching a silent movie or to attentively discriminate the different sounds. In both musicians and non-musicians, the pre-attentively evoked mismatch negativity (MMN) component was larger to slight changes in music than in speech sounds. The MMN was also larger to intensity changes in music sounds and to duration changes in speech sounds. During attentional listening, all subjects more readily discriminated changes among speech sounds than among music sounds as indexed by the N2b response strength. Furthermore, during attentional listening, musicians displayed larger MMN and N2b than non-musicians for both music and speech sounds. Taken together, the data indicate that the discriminative abilities in human audition differ between music and speech sounds as a function of the sound-change context and the subjective familiarity of the sound parameters. These findings provide clear evidence for top-down modulatory effects in audition. In other words, the processing of sounds is realized by a dynamically adapting network considering type of sound, expertise and attentional demands, rather than by a strictly modularly organized stimulus-driven system.

Sequential effects of propofol on functional brain activation induced by auditory language processing: an event-related functional magnetic resonance imaging study.

BACKGROUND: We have investigated the effect of propofol on language processing using event-related functional magnetic resonance imaging (MRI). METHODS: Twelve healthy male volunteers underwent MRI scanning at a magnetic field strength of 3 Tesla while performing an auditory language processing task. Functional images were acquired from the perisylvian cortical regions that are associated with auditory and language processing. The experiment consisted of three blocks: awake state (block 1), induction of anaesthesia with 3 mg kg(-1) propofol (block 2), and maintenance of anaesthesia with 3 mg kg(-1) h(-1) propofol (block 3). During each block normal sentences and pseudo-word sentences were presented in random order. The subjects were instructed to press a button to indicate whether a sentence was made up of pseudo-words or not. All subjects stopped responding during block two. The data collected before and after the subjects stopped responding during this block were analyzed separately. In addition, propofol plasma concentrations were measured and the effect-site concentrations of propofol were calculated. RESULTS: During wakefulness, language processing induced brain activation in a widely distributed temporofrontal network. Immediately after unresponsiveness, activation disappeared in frontal areas but persisted in both temporal lobes (block 2 second half, propofol effect-site concentration: 1.51 microg ml(-1)). No activation differences related to the task were observed during block 3 (propofol effect-site concentration: 4.35 microg ml(-1)). CONCLUSION: Our findings suggest sequential effects of propofol on auditory language processing networks. Brain activation firstly declines in the frontal lobe before it disappears in the temporal lobe.

An electrophysiological response to different pitch contours in words.

A spoken word with more than one syllable contains a specific stress pattern found to be processed during spoken word recognition. The present study investigated the word's pitch contour as a single auditory parameter that marks stress. Event-related brain potentials (ERPs) were recorded while subjects made decisions to artificially pitch manipulated words. ERPs revealed that pitch contours are discriminated already within the first syllable of a word. Furthermore, behavioral responses for words with incorrect pitch contours were longer than for words with correct pitch contours. The results suggest that the pitch contour is an auditory feature of the spoken word that a listener automatically processes during spoken word recognition.

The protease inhibitors.

With the advent of newer antiretroviral agents for the treatment of patients with human immunodeficiency virus (HIV) infection and acquired immune deficiency syndrome (AIDS), health care providers are faced with many options to optimize their patients' therapy. Currently, there are three groups of drugs available for the treatment of patients with HIV infection: nucleoside reverse transcriptase inhibitors (also known as nucleoside analogues), nonnucleoside reverse transcriptase inhibitors, and protease inhibitors (PIs). The preferred initial treatment regimen now consists of two nucleoside analogues and a PI. Protease inhibitors cause profound and sustained suppression of viral replication, increase time to first AIDS-defining illness, and reduce mortality. Each of the available PIs have distinct pharmacokinetic and metabolic properties that result in different dosing regimens and potential for interactions with food and other drugs. Patients with HIV infection typically receive several drugs; therefore, convenience of administration, optimal side-effect profile, and cost of the agents must also be considered along with the potential for drug interactions.A growing proportion of HIV patients worldwide are women. HIV-infected pregnant women should be offered antiretroviral prophylaxis to prevent perinatal HIV transmission as well as to optimize their own health. Zidovudine (ZDV) treatment has been the standard antiretroviral treatment during pregnancy; however, recent data has shown that combination regimens produce a more pronounced antiviral effect and may be more effective than ZDV monotherapy in preventing perinatal HIV transmission.

Lateralization of prosody during language production: a lesion study.

To examine brain lateralization of prosody during speech, the sentence production of six right-hemisphere-lesion patients and five left-hemisphere-lesion patients was compared to that of seven normal controls using a question-answer paradigm. The task required the prosodic realization of two different syntactic structures under conditions of wide and narrow focus. Acoustical analyses were carried out on F0 and time structure. These analyses revealed a preserved ability in patients to express differences in syntactic structure via prosody. However, there were deficits in distinguishing narrow focus from wide focus. Whereas both right- and left-hemisphere lesions caused impairments in the realization of F0, time structure was mainly impaired in left-hemisphere patients. Therefore, the present results from language production support functional as well as cue-dependent hypotheses of the lateralization of prosodic processing in the brain.

Brain potentials indicate immediate use of prosodic cues in natural speech processing.

Spoken language, in contrast to written text, provides prosodic information such as rhythm, pauses, accents, amplitude and pitch variations. However, little is known about when and how these features are used by the listener to interpret the speech signal. Here we use event-related brain potentials (ERP) to demonstrate that intonational phrasing guides the initial analysis of sentence structure. Our finding of a positive shift in the ERP at intonational phrase boundaries suggests a specific on-line brain response to prosodic processing. Additional ERP components indicate that a false prosodic boundary is sufficient to mislead the listener's sentence processor. Thus, the application of ERP measures is a promising approach for revealing the time course and neural basis of prosodic information processing.

Tapping in to new technology. Close links to patients at home.

This telecommunications system contacts home care patients automatically for followup using clinically developed software and a standard touch-tone phone. This system could help control costs by allowing health professionals to monitor patients' progress without unnecessary visits.

Postoperative infection caused by an unusual serotype of Streptococcus pneumoniae associated with multiple drug resistance.

A 15-month-old child developed an infectious pulmonary complication of open heart surgery. Cultures of the respiratory secretions showed growth of a 9L serotype of Streptococcus pneumoniae which was resistant to penicillin, tetracycline, and chloramphenicol. There was no evidence that the organism was spread among the family of the patient or hospital personnel.