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PubMed2004

Comparison of poly-N-acetyl glucosamine with commercially available topical hemostats for achieving hemostasis in coagulopathic models of splenic hemorrhage.

BACKGROUND: The hemostatic quality of the poly-N-acetyl glucosamine (p-GlcNAc) patch was compared with a fibrin sealant, fibrin bandage, and cellulose patch. METHODS: A 2 x 2-cm capsular strip to a depth of 3 mm of the swine spleen was used as a source of bleeding. Splenic lacerations were created in hemophilia B dogs and treated with p-GlcNAc and Surgicel. Wounds were created in rabbits and treated with p-GlcNAc at 37degreesC and after keeping body core temperature at 29degreesC. RESULTS: Poly-N-acetyl glucosamine was able to achieve hemostasis with greater efficacy than either of the fibrin-based bandages. In the hemophilia B dog study, p-GlcNAc significantly outperformed Surgicel, with p-GlcNAc achieving hemostasis in 75% of the treated wounds compared with 17% for the cellulose patch. The hypothermia study demonstrated that p-GlcNAc is equally effective at 29degreesC and at 37degreesC. CONCLUSION: Poly-N-acetyl glucosamine was effective at controlling bleeding in animals with experimentally induced or genetic coagulopathic disorders.

Acetylglucosamine↗

PubMed2005

Impairment of syntax and lexical semantics in a patient with bilateral paramedian thalamic infarction.

Bilateral vascular thalamic lesions are rare. Although a variety of neurobehavioral manifestations have been described, the literature is less documented with regard to accompanying linguistic disturbances. This article presents an in-depth neurolinguistic analysis of the language symptoms of a patient who incurred bilateral paramedian ischemic damage of the thalamus. In the post-acute phase of the stroke, a unique combination of transcortical sensory aphasia with syntactic impairment was found. Because of this atypical semiological association, additional analyses of spontaneous speech were performed. In spite of the typological affinity with the grammatic characteristic of marked simplification of syntax observed in Broca's aphasia, only a wordclass specific, lexical-semantic deficit for verbs was objectified. The hypothesis that lexical-semantic disturbances in our patient might result from a functional deafferentiation of both thalami with the frontal lobe is supported by: (1) associated neuropsychological deficits of frontal origin and (2) frontal-like behavioral disturbances.

Aged↗

PubMed2003

Olfaction and depth of word processing: a magnetoencephalographic study.

Using a whole-cortex magnetoencephalograph, magnetic field changes were recorded to describe brain activities related to simultaneous visual and olfactory processing and to detect odor-related influences on verbal information processing. Words had to be either shallowly (nonsemantic) or deeply (semantic) encoded by healthy young subjects, each of these tasks under two different kinds of olfactory stimulation. After each encoding phase, word recognition performance was tested. First, the odor was randomly associated with some of the study words (simultaneous stimulation; same duration as for words) for both depths of word processing conditions, and second, continuous olfactory stimulation (permanent stimulation) was provided during the whole study phases of both depths of word processing conditions. The statistical analysis of the physiological data revealed evidence of a specific odor-induced effect depending on depth of word processing and kind of olfactory stimulation. Brain activity between about 250 and 450 ms as well as between about 650 and 1000 ms after stimulus onset was found to vary as a function of odor delivery and depth of word processing. In addition, a significant effect of odor stimulation on subsequent word recognition performance occurred in case of simultaneous odor stimulation and semantic word encoding. It is interpreted that in this case, word recognition performance significantly decreased because of the presence of the odor during prior word encoding. Such a behavioral effect was missing in all other conditions. The present psychological and physiological findings support the idea that semantic word encoding is specifically affected by simultaneous olfactory information processing. It is concluded that this phenomenon is due to a competition with cortical regions related to language and olfactory information processing, as suggested by T. S. Lorig (1999, Neurosci. Biobehav. Rev. 23, 391-398).

Adult↗

PubMedDate not supplied

Diving behaviour of a reptile (Crocodylus johnstoni) in the wild: interactions with heart rate and body temperature.

The differences in physical properties of air and water pose unique behavioural and physiological demands on semiaquatic animals. The aim of this study was to describe the diving behaviour of the freshwater crocodile Crocodylus johnstoni in the wild and to assess the relationships between diving, body temperature, and heart rate. Time-depth recorders, temperature-sensitive radio transmitters, and heart rate transmitters were deployed on each of six C. johnstoni (4.0-26.5 kg), and data were obtained from five animals. Crocodiles showed the greatest diving activity in the morning (0600-1200 hours) and were least active at night, remaining at the water surface. Surprisingly, activity pattern was asynchronous with thermoregulation, and activity was correlated to light rather than to body temperature. Nonetheless, crocodiles thermoregulated and showed a typical heart rate hysteresis pattern (heart rate during heating greater than heart rate during cooling) in response to heating and cooling. Additionally, dive length decreased with increasing body temperature. Maximum diving length was 119.6 min, but the greatest proportion of diving time was spent on relatively short (<45 min) and shallow (<0.4 m) dives. A bradycardia was observed during diving, although heart rate during submergence was only 12% lower than when animals were at the surface.

Activity Cycles↗

PubMed1989

Computer analysis of manometric recordings. A study of overnight rectal activity in normal children.

To read and analyze manometric tracings from selected biological systems, a computer program was produced using low cost personal computer hardware. The program contains facilities for automatic scoring of contractions, intercontractile intervals (modality) and frequency analysis. This report concerns analysis of two overnight rectal motility recordings in 11 normal teenagers. After A/D conversion of data the developed software offers a set of options i.e. automatized scoring of contraction, detection of intervals between contractions and analytical tools such as histographic presentation of data, and presentation in the time domain. The A/D conversion time and computer analysis time for an 8 hour recording was 15 and 13 minutes, respectively. The analysis of frequency distribution overnight showed for the material as a whole 63% of no activity, 33% of 0-2 contractions x min-1 and 4% of more than 2 contractions x min-1. Modality analysis showed a peak between 15 and 25 seconds. Approximately 30% of the tracings showed accumulated intervals, which were multiples of the peak. No significant correlation was found between the first and second night of observation regarding the number of contractions and maximum frequency overnight. Significant correlation was found for the number of periods with high frequency activity between the two nights (p less than 0.05). Long-term pressure activity can be analyzed using the presented computer-aided method, providing a rapid and objective measurement of classical parameters and access to more in-depth analysis. This actual study of normal overnight rectal activity showed a large inter- and intra-individual variation.

Adolescent↗

PubMed2003

Magnetoencephalographic--features related to mild cognitive impairment.

We recorded changes of brain activity from 10 MCI patients and 10 controls related to shallow (nonsemantic) and deep (semantic) word encoding using a whole-head MEG. During the following recognition tasks, all participants had to recognize the previously encoded words, which were presented again together with new words. In both groups recognition performance significantly varied as a function of depth of processing. No significant differences were found between the groups. Reaction times related to correctly classified new words (correct rejections) and incorrectly classified repetitions (misses) of MCI patients showed a strong tendency toward prolongation compared to controls, although no statistically significant differences occurred. Strikingly, in patients the neurophysiological data associated with nonsemantic and semantic word encoding differed significantly between 250 and 450 ms after stimulus onset mainly over left frontal and left temporal sensors. They showed higher electrophysiological activation during shallow encoding as compared to deep encoding. No such significant differences were found in controls. The present results might reflect a dysfunction with respect to shallow encoding of visually presented verbal information. It is interpreted that additional neural activation is needed to compensate for neurodegeneration. This finding is suggested to be an additional tool for MCI diagnosis.

Aged↗

PubMed2026

No receptor-binding domain adaptation detected in within-host H5N1 surveillance of 4,559 US dairy outbreak sequences.

BACKGROUND: The 2024-2026 US H5N1 clade 2.3.4.4b dairy cattle outbreak has been characterised primarily through consensus-level phylogenetics. Whether mammalian-adaptation variants are emerging at sub-consensus frequencies within infected hosts, particularly at the haemagglutinin receptor-binding domain (RBD), remains unknown because no systematic within-host variant analysis of the public sequencing corpus has been performed. METHODS: We conducted a pre-registered, corpus-wide intrahost single-nucleotide variant (iSNV) analysis of all publicly available H5N1 cattle, feline-spillover, and retail-milk sequences on the NCBI Sequence Read Archive (4559 samples across 7 BioProjects). A dual-caller concordance pipeline (iVar + LoFreq) with empirically determined allele frequency (AF) threshold (3%, set via four-criterion validation including synthetic spike-in controls) was applied to an 11-site Tier 1 mammalian-adaptation panel spanning the polymerase complex, haemagglutinin RBD, and accessory proteins. Within-host nucleotide diversity was compared across host categories. RESULTS: The HA RBD sites Q226L and G228S (H3 numbering) showed zero detections across >4300 adequately sequenced samples at all AF thresholds tested (1-5%), despite the pipeline detecting other non-synonymous variants at these exact codon positions (upper 95% CI for prevalence: 0.08%). Seven of eleven adaptation sites carried statistically significant iSNV signals after Bonferroni correction (corrected α = 0.00417), though all at low prevalence (≤2.95%). Genotype stratification showed that most polymerase-site detections reflected genotype structure rather than within-host emergence: the apparent PB2 631 L→M "reversion" was largely the ancestral avian state of the D1.1 genotype (20 of 23 detections), which never acquired the 631L mammalian adaptation, with only two genuine sub-consensus events in the B3.13 background, while consensus-level PB2 701N was a fixed feature of the D1.1 genotype (10 of 14 detections) rather than independent sub-consensus emergence. Cattle exhibited significantly higher within-host nucleotide diversity than feline-spillover samples (π = 1.59 × 10-4 vs 6.11 × 10-5; Kruskal-Wallis p = 6.6 × 10-15), a finding that persisted after depth-matching (p = 4.6 × 10-5); this may reflect prolonged mammary-gland infection, though sampling differences and host biology cannot be excluded. CONCLUSIONS: We did not detect HA receptor-switching adaptation (the acquisition of human-type α2,6 receptor binding via Q226L/G228S) at any tested allele frequency in the US dairy H5N1 outbreak. Sub-consensus mammalian-adaptation signals exist at polymerase-complex sites but at low prevalence, are genotype-structured rather than independently recurrent, and require functional characterisation before informing risk assessment.

Dairy cattle↗

PubMed2005

Effects of display medium and luminance contrast on concept formation and EEG response.

Reading from a visual display terminal (VDT) has increased enormously with widespread computer use. Whether such reading affects higher cognitive processes requires study so the effect of display medium (LCD screen vs paper) and luminance contrast (1:3, 1:7, 1:11) on concept-formation performance and EEG responses was investigated. 96 men and 24 women participated in two concept-formation tasks (rule learning vs attribute and rule learning). Concept-formation performance and EEG responses were similar for stimuli displayed on paper or LCD screen. The concern that the screen may be detrimental to conception-formation performance was not confirmed; however, luminance contrast significantly affected time to complete a concept-formation task and EEG response. The middle contrast (1:7) had the smallest mean EEG power, so this contrast might be appropriate for cognitive performance. Participants' performance was significantly faster and EEG power lower for the rule-learning task than for an attribute and rule-learning task.

Adult↗

PubMed1997

Molecular analyses of the sediment of the 11,000-m deep Mariana Trench.

We have obtained sediment samples from the world's deepest sea-bottom, the Mariana Trench challenger point at a depth of 10,898 m, using the new unmanned submersible Kaiko. DNA was extracted from the sediment, and DNA fragments encoding several prokaryotic ribosomal RNA small-subunit sequences and pressure-regulated gene clusters, typically identified in deep-sea adapted bacteria, were amplified by the polymerase chain reaction. From the sequencing results, at least two kinds of bacterial 16S rRNAs closely related to those of the genus Pseudomonas and deep-sea adapted marine bacteria, and archaeal 16S rRNAs related to that of a planktonic marine archaeon were identified. The sequences of the amplified pressure-regulated clusters were more similar to those of deep-sea barophilic bacteria than those of barotolerant bacteria. These results suggest that deep-sea adapted barophilic bacteria, planktonic marine archaea, and some of the world's most widespread bacteria (the genus Pseudomonas) coexist on the world's deepest sea-bottom.

Base Sequence↗

PubMed1989

Clock drawing in Alzheimer's disease. A novel measure of dementia severity.

We have tested a simple and reliable measure of visuospatial ability in Alzheimer patients--the Clock Drawing Test. To determine the usefulness of this measure, we asked 67 Alzheimer patients and 83 normal controls to draw the face of a clock reading the time of 2:45. Six independent observers blindly evaluated the results with ratings from 10 (best) to 1 (worst). The mean performance score of Alzheimer subjects was 4.9 +/- 2.7 compared to 8.7 +/- 1.1 for normal controls (P less than .001). Inter-rater reliability for the clocks drawn by Alzheimer patients was highly significant (r = 0.86; P less than .001), and there was relatively little overlap between ratings for Alzheimer patients and normal controls. Furthermore, correlations were highly significant (P less than .001) between the mean score of clock drawings and three independent global measures of dementia severity. Although the Clock Drawing Test is certainly not a definitive indicator of Alzheimer's disease, the test is easy to administer and provides a useful measure of dementia severity for both research and office settings where sophisticated neuropsychological testing is not available.

Aged↗

PubMed1997

The accuracy of the CAGE, the Brief Michigan Alcoholism Screening Test, and the Alcohol Use Disorders Identification Test in screening trauma center patients for alcoholism.

OBJECTIVE: To evaluate the accuracy of questionnaire screening instruments to identify lifetime alcohol dependence among trauma center patients. METHODS: The study was conducted at a Level I trauma center between September 1994 and November 1996. Patients meeting eligibility requirements (> or = 18 years old, admission from injury scene, > or = 2 days of hospitalization, intact cognition) were evaluated for alcohol abuse and dependence. Screening instruments consisted of the CAGE, the Brief Michigan Alcoholism Screening Test, and the Alcohol Use Disorders Identification Test. Screening results were compared with lifetime alcohol dependence diagnoses made using the in-depth Psychoactive Substance Use Disorders section of the Structured Clinical Interview. Accuracy was quantified as sensitivity, specificity, positive/negative predictive values, and receiver operating characteristic curves (used to calculate area under the curve). RESULTS: Of the 1,118 patients studied, lifetime alcohol dependence was diagnosed by Structured Clinical Interview in 397 (35.5%), and abuse was diagnosed in 90 (8.1%) others. The CAGE was the best predictor of lifetime alcohol dependence, i.e., had the largest area under the curve (93%) and the highest sensitivity (84%), specificity (90%), positive predictive value (82%), and negative predictive value (91%). Among patients testing positive for alcohol, 63% had a lifetime alcohol dependence diagnosis. CONCLUSION: The CAGE is an efficient screening test to detect alcohol dependence in trauma center populations. It should be used in combination with alcohol testing to identify patients at risk of alcohol use problems.

Adolescent↗

PubMed2006

Genome variation and evolution of the malaria parasite Plasmodium falciparum.

Infections with the malaria parasite Plasmodium falciparum result in more than 1 million deaths each year worldwide. Deciphering the evolutionary history and genetic variation of P. falciparum is critical for understanding the evolution of drug resistance, identifying potential vaccine candidates and appreciating the effect of parasite variation on prevalence and severity of malaria in humans. Most studies of natural variation in P. falciparum have been either in depth over small genomic regions (up to the size of a small chromosome) or genome wide but only at low resolution. In an effort to complement these studies with genome-wide data, we undertook shotgun sequencing of a Ghanaian clinical isolate (with fivefold coverage), the IT laboratory isolate (with onefold coverage) and the chimpanzee parasite P. reichenowi (with twofold coverage). We compared these sequences with the fully sequenced P. falciparum 3D7 isolate genome. We describe the most salient features of P. falciparum polymorphism and adaptive evolution with relation to gene function, transcript and protein expression and cellular localization. This analysis uncovers the primary evolutionary changes that have occurred since the P. falciparum-P. reichenowi speciation and changes that are occurring within P. falciparum.

Animals↗

PubMed2003

An fMRI study of semantic processing in men with schizophrenia.

As a means toward understanding the neural bases of schizophrenic thought disturbance, we examined brain activation patterns in response to semantically and superficially encoded words in patients with schizophrenia. Nine male schizophrenic and 9 male control subjects were tested in a visual levels of processing (LOP) task first outside the magnet and then during the fMRI scanning procedures (using a different set of words). During the experiments visual words were presented under two conditions. Under the deep, semantic encoding condition, subjects made semantic judgments as to whether the words were abstract or concrete. Under the shallow, nonsemantic encoding condition, subjects made perceptual judgments of the font size (uppercase/lowercase) of the presented words. After performance of the behavioral task, a recognition test was used to assess the depth of processing effect, defined as better performance for semantically encoded words than for perceptually encoded words. For the scanned version only, the words for both conditions were repeated in order to assess repetition-priming effects. Reaction times were assessed in both testing scenarios. Both groups showed the expected depth of processing effect for recognition, and control subjects showed the expected increased activation of the left inferior prefrontal cortex (LIPC) under semantic encoding relative to perceptual encoding conditions as well as repetition priming for semantic conditions only. In contrast, schizophrenics showed similar patterns of fMRI activation regardless of condition. Most striking in relation to controls, patients showed decreased LIFC activation concurrent with increased left superior temporal gyrus activation for semantic encoding versus shallow encoding. Furthermore, schizophrenia subjects did not show the repetition priming effect, either behaviorally or as a decrease in LIPC activity. In patients with schizophrenia, LIFC underactivation and left superior temporal gyrus overactivation for semantically encoded words may reflect a disease-related disruption of a distributed frontal temporal network that is engaged in the representation and processing of meaning of words, text, and discourse and which may underlie schizophrenic thought disturbance.

Adult↗

PubMed1998

In situ calibration of miniature sensors implanted into the anterior cruciate ligament part II: force probe measurements.

The arthroscopically implantable force probe transducer, which measures the effects of local ligament fiber tension, was inserted into the anteromedial band of the anterior cruciate ligament after measurements with the differential variable reluctance transducer were completed in Part I of this study. The overall goals in Part II remained the same, with additional experiments included to determine the sensitivity of output voltage from the transducer to medial-lateral placement of the device within the anteromedial band and to depth of placement within a given insertion hole. Calibration curves of output voltage from the arthroscopically implantable force probe transducer versus resultant force in the ligament were generated during a separate series of knee-loading experiments identical to those performed in Part I. The output voltage for a given probe placement was highly sensitive to the depth of implantation into the anteromedial band. When the probe was completely buried within the ligament, voltage outputs were often sporadic or absent even though surface fibers had clearly developed tension. When the probe was only partially inserted into the hole, such that the end of the probe was slightly proud to the surface, voltage output was significantly higher as the device measured tension in the superficial fibers. Voltage outputs for proud placement were always significantly higher than corresponding voltages for deep placements for all test conditions. With proud placements, voltage outputs were not sensitive to small deviations in medial-lateral position within the anteromedial band. Mean coefficients of variation for output voltage (four repeated placements of the probe into the same central hole) ranged from 0.156 to 0.359 (deep and proud insertions). Output voltage from the probe generally followed the pattern of resultant force in the ligament during passive knee extension. For anterior tibial loading, the contribution of deep fibers to resultant force did not depend on the knee flexion angle at which the test was conducted; the contribution of superficial fibers was greatest beyond 45 degrees of flexion and least at full extension. The contributions of the anteromedial band to resultant force in the ligament were not significantly different between the three modes of loading (anterior tibial force, internal tibia torque, and varus moment) at either 0 or 10 degrees of flexion; this was true for both superficial and deep fibers. We found it necessary to secure the probe within the insertion site using a suture (for both deep and proud placements) to obtain repeatable readings. Puncturing the anteromedial band clearly produced tissue damage; the insertion hole often produced a permanent plane of cleavage in the anteromedial band. However, this tissue damage did not alter the overall ability of the ligament to generate resultant force.

Aged↗

PubMed1985

Differential cerebral involvement in perceiving Chinese characters: levels of processing approach.

Three experiments were designed to determine the accuracy and latency with which right-handed Chinese university students (12 females and 12 males) recognized Chinese characters in the left and right visual half-fields (VHFs). The experiments varied in the "depth" of processing required. Experiment 1 was a lexical decision task in which the configuration of the stimulus (a real Chinese character or the mirror image of a real character) determined whether the grapheme was an actual character. Experiment 2 required phonological processing; i.e., subjects had to decide whether a character (or a foil) matched the sound of an orally presented Chinese character. Experiment 3 required semantic processing; i.e., subjects had to decide if a character (or a foil) belonged to a particular semantic category. In each experiment, single characters were presented unilaterally for 150 msec. There was a significant right VHF superiority for accuracy scores for Experiments 2 and 3 but not for Experiment 1. None of the experiments yielded significant visual asymmetries in reaction time. The results do not support previous claims of orthography-specific laterality, but instead show that laterality effects for morphemic stimuli vary with the orthographic, phonological, and semantic processing demands of the task.

Adult↗

PubMed2003

Unique physiological and pathogenic features of Leptospira interrogans revealed by whole-genome sequencing.

Leptospirosis is a widely spread disease of global concern. Infection causes flu-like episodes with frequent severe renal and hepatic damage, such as haemorrhage and jaundice. In more severe cases, massive pulmonary haemorrhages, including fatal sudden haemoptysis, can occur. Here we report the complete genomic sequence of a representative virulent serovar type strain (Lai) of Leptospira interrogans serogroup Icterohaemorrhagiae consisting of a 4.33-megabase large chromosome and a 359-kilobase small chromosome, with a total of 4,768 predicted genes. In terms of the genetic determinants of physiological characteristics, the facultatively parasitic L. interrogans differs extensively from two other strictly parasitic pathogenic spirochaetes, Treponema pallidum and Borrelia burgdorferi, although similarities exist in the genes that govern their unique morphological features. A comprehensive analysis of the L. interrogans genes for chemotaxis/motility and lipopolysaccharide synthesis provides a basis for in-depth studies of virulence and pathogenesis. The discovery of a series of genes possibly related to adhesion, invasion and the haematological changes that characterize leptospirosis has provided clues about how an environmental organism might evolve into an important human pathogen.

Bacterial Adhesion↗

PubMed2025

A vision of how low-coverage sequence data should contribute to genetic evaluation in the future.

Low-coverage sequencing refers to sequencing DNA of individuals to a low depth of coverage (e.g., 0.5X) and imputing that sequence to a genomic sequence based on reference haplotypes from individuals sequenced to a high depth of coverage (e.g., ≥10X). It has been proposed as an alternative to genotyping by Single-nucleotide polymorphisms (SNP) arrays. At least one commercial product based on it is available for agricultural species. Concerns limiting adoption in its current form are: 1) the cost of storing the huge volume of data it generates and 2) whether that additional data will result in improved accuracy of genetic evaluation. This work envisions future implementation of low-coverage sequencing to reduce storage costs and enhance genetic evaluations by leveraging the additional information in the full sequence of the pangenome to account for more genetic variation. We propose addressing the storage issue by representing genomic sequence of an individual in a pair of haplotype arrays with each element pointing to an enumerated haplotype of the sequence within one of approximately 50,000 defined genome segments. Assuming 60 million genomic variants, the infrastructure required to translate the identifier of any enumerated haplotype into its genomic sequence would require less than 10 gigabytes of binary storage. Each haplotype array element would require 2 bytes, so the marginal binary storage required to represent the genomic sequence of an individual would be about 200 kilobytes (KB), similar to the genotypes from a SNP array with 200,000 markers. This assumes no pedigree and no ambiguity of the imputation, though the latter is unrealistic. Strategies to minimize, and when necessary, to manage and efficiently represent ambiguity are proposed. The genomic sequence of an individual could be stored in about 1 KB (binary) if both parents have unambiguous sequences stored as described above. The proposed system for representing the pangenome includes algorithms for read mapping and imputation intended to leverage all known genetic variation in the target population. It is also designed to use sequencing reads generated for imputing the genomic sequence of new individuals to identify unrecognized mutations, crossovers, and structural variants, thus continuously improving the genome representation, especially if widespread use of low-coverage sequencing in livestock industries is realized. This could make improved genetic merit and management of livestock feasible without computational burden.

Animals↗

PubMed1995

Chest wall responses to rebreathing in halothane-anesthetized dogs.

BACKGROUND: The pattern of respiratory muscle use during halothane-induced anesthesia differs markedly among species breathing quietly. In humans, halothane accentuates phasic activity in rib cage and abdominal expiratory muscles, whereas activity in the parasternal intercostal muscles is abolished. In contrast, halothane abolishes phasic expiratory muscle activity during quiet breathing in dogs, but parasternal muscle activity is maintained. Respiratory muscle responses to CO2 rebreathing were measured in halothane-anesthetized dogs to determine if species differences present during quiet breathing persist over a wide range of central respiratory drive. METHODS: Chronic electromyogram electrodes were implanted in three expiratory agonists (the triangularis sterni, transversus abdominis, and external oblique muscles) and three inspiratory agonists (the parasternal intercostal muscle, costal and crural diaphragm) of six mongrel dogs. After a 1-month recovery period, the dogs were anesthetized in the supine position with halothane. The rebreathing response was determined by Read's method during anesthesia with stable 1 and 2 minimum alveolar end-tidal concentrations of halothane. CO2 concentrations were measured in the rebreathing bag using an infrared analyzer. Chest wall motion was measured by fast three-dimensional computed tomographic scanning. RESULTS: Halothane concentration did not significantly affect the slope of the relationship between minute ventilation (VE) and PCO2 (0.34 +/- 0.04 [M +/- SE] and 0.28 +/- 0.05 l.min-1.mmHg-1 during 1 and 2 minimum alveolar concentration anesthesia, respectively). However, 2 minimum alveolar concentration anesthesia did significantly decrease the calculated VE at a PCO2 of 60 mmHg (from 7.4 +/- 1.2 to 4.0 +/- 0.6 l.min-1), indicating a rightward shift in the response relationship. No electromyographic activity was observed in any expiratory muscle before rebreathing. Rebreathing produced electromyographic activity in at least one expiratory muscle in only two dogs. Rebreathing significantly increased electromyographic activity in all inspiratory agonists. Rebreathing significantly increased inspiratory thoracic volume change (delta Vth), with percentage of delta Vth attributed to outward rib cage displacement increasing over the course of rebreathing during 1 minimum alveolar concentration anesthesia (from 33 +/- 6% to 48 +/- 2% of delta Vth). CONCLUSIONS: Rebreathing did not produce expiratory muscle activation in most dogs, demonstrating that the suppression of expiratory muscle activity observed at rest persists at high levels of ventilatory drive. Other features of the rebreathing response also differed significantly from previous reports in halothane-anesthetized humans, including (1) an increase in the rib cage contribution to tidal volume during the course of rebreathing, (2) recruitment of parasternal intercostal activity by rebreathing, (3) differences in the response of ventilatory timing, and (4) the lack of effect of anesthetic depth on the slope of the ventilatory response. These marked species differences are further evidence that the dog is not a suitable model to study anesthetic effects on the activation of human respiratory muscles.

Anesthetics, Inhalation↗