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Biomedical subjects

W G Hall

Publications and source records attributed to W G Hall.

At least 19 recordsLinked to original sources
PubMed1998

Electromyographic analysis of oral habituation in rat pups.

Rat pups show decreases in mouthing activity in response to a series of repeated oral infusions of a diet. This decrease in mouthing activity has been termed "oral habituation" and these changes have been readily recorded with simple behavioral observations. Oral habituation appears to be a component of satiety in young rats. In the present study, to more specifically characterize changes in motor response topography during habituation in muscle groups used for mastication, mouthing activity was recorded by implanting fine wire electromyographic electrodes in the superficial masseter, anterior digastric, sternohyoideus, and genioglossus muscles of 12-day-old rat pups. During testing, pups received a series of brief oral infusions of a 10% sucrose diet delivered through an oral cannula. The results demonstrated that mouthing activity as observed and scored behaviorally was highly correlated with mouthing behavior recorded by EMG, with oral habituation distinctly emerging in both measures. In addition, the pattern of motor activity in the four masticatory muscles changed during the course of oral habituation. Within the minute following a single infusion, the cycle frequency, duration of activity, and relative onset time of activity in the four muscles changed. In addition, across the course of habituation, both cycle frequency and relative onset times of muscle activity changed. These results demonstrate the general reliability of behavioral observations of masticatory motor activity in young rats and provide further information on how the pattern of activity of muscles involved in the mouthing motor pattern is altered during the course of oral habituation.

Animals↗
PubMed1997

Sensitization of ingestive responding in preweanling rats: time course and specificity.

Two experiments measured the response-enhancing effects of oral stimulation in young rats with no feeding experience. In Experiment 1, pups were implanted with oral cannulas and deprived for 0, 6, or 24 hr. In nondeprived rats, sucrose exposure transiently sensitized oral responding to subsequent stimuli for several minutes. Among 24-hr-deprived rats, baseline oral responding had increased to where sucrose exposure was no longer sensitizing. Unlike oral responding, sensitization of activity by sucrose exposure increased with deprivation. Sensitization was also evident in the microstructure of responses to infusions. In Experiment 2, the specificity of sensitization was examined by varying stimulus palatability. Sucrose exposure sensitized oral responding to both sucrose and quinine-adulterated sucrose, but quinine-adulterated sucrose was not sensitizing. The results suggest that in inexperienced rats, oral stimulation initiates changes in responding that may mimic the endogenous sequelae of deprivation, perhaps representing early substrates for learned controls of intake.

Animals↗
PubMed1995

Unilateral conditioning of an odor aversion in 6-day-old rat pups.

In young rats, several forms of olfactory memory can be functionally localized to one side of the brain by restricting training stimuli to one naris and corresponding olfactory bulb. In the experiment, the analysis of lateralized olfactory learning in 6-day-old rat pups was extended by an evaluation of the consequences of aversive reinforcers in a unilateral olfactory conditioning paradigm. An olfactory aversion was conditioned by delivering a mild footshock to animals in the presence of a novel odor. Olfactory stimulation was confined to one naris and corresponding olfactory bulb by inserting a soft rubber plug into the opposite naris. This lateralization in processing resulted in unilateral memory for the odor aversion that was only expressed when the trained naris was open during an odor preference test. The hypothesis that the hedonic value (or valence) component of conditioning is represented in structures that are unilaterally accessed during training and testing is discussed.

Animals↗
PubMed1995

Evaluation of a distance consulting service based on interactive video and integrated computerized technology.

Telemedicine equipment was installed at a rural site in Drumheller and at Calgary, 85 miles (136 km) away. It allowed consultation between health-care providers at Drumheller and specialists and subspecialists at the Faculty of Medicine in Calgary. The efficacy of the system in providing more equitable access to health care for persons living in geographically remote sites was evaluated during a 12-month pilot project. Seventy-five encounters were attempted during the study. A total of 55 encounters (42 clinical and 13 non-clinical) were completed. The completed clinical encounters were distributed across a wide spectrum of medical specialties. Users of the system reported favourably on the impact of the telemedicine system on access to health services for rural patients, on diagnostic, investigative and management decisions, on patient and physician travel times, on feelings of professional isolation and educational opportunities and on overall patient health status. The study provides new knowledge and demonstrates the success of the technology in this project. As expected, other problems were raised and addressed in a preliminary manner including: the potential for health-provider education; acquisition and retention of rural physicians; ethical, legal and patient confidentiality issues; minimum acceptable technology; and network management issues.

Canada↗
PubMed1995

The use of advanced computer technology to enhance access to health care and to respond to community needs: the results of the evaluation of a technology-based clinical consultation service.

This paper describes a long distance, high tech, two-way interactive video pilot system that supports teleconsultations between primary health care givers at a rural site and specialists and subspecialists at the Faculty of Medicine, University of Calgary. Evaluation results from the 12-month trial are presented. The underlying philosophy behind the telemedicine outreach pilot program was to provide equal access to health services for those currently in under-served areas. The advanced technology system offered multiple clinical services in emergency, urgent, and elective situations. The impact of the telemedicine consultative service on health care delivery, patients, providers, and costs were evaluated. Findings from the 12-month trial demonstrate that quality care and access to care can be offered in spite of the disparate location of patients and health care providers. Some limitations and constraints to the implementation of the technology are noted and reviewed.

Alberta↗
PubMed1994

Does oral experience terminate ingestion?

Using data from studies of ingestive behavior in developing rat pups we demonstrate how oral experience can contribute to the termination of ingestion. In rat pups, repeated oral stimulation with sweet solutions causes a decline in oral responsiveness. The diminished responsiveness is specific to the flavor of the stimulus experienced orally and can persist for several hours. We suggest that this experience-based decrement in responsiveness is best considered "oral habituation" and that oral habituation largely accounts for the onset of satiety. Post-ingestive feedback signals may have their influence through the oral habituation process or act in the context of oral habituation. Oral habituation is also shown to depend on the pattern of stimulus presentation, a phenomenon that adds considerable complexity to assessing the contributions of oral experience to satiety. The concept of oral habituation may be useful in understanding the immediate control of ingestion and the moment-to-moment expression of ingestive behavior in adult animals.

Animals↗
PubMed1993

Taste and smell sensations enhance the satiating effect of both a high-carbohydrate and a high-fat meal in humans.

The effects of meal sensory properties (tasty vs. bland) and nutrient composition [high-CHO (carbohydrate) vs. high-FAT] on hunger ratings, blood glucose and free fatty acids (FFA), taste perception, and subsequent food intake, were studied in human subjects. Aspartame and vanilla were used to augment meal palatability, yielding four isocaloric liquid meals: bland-FAT, tasty-FAT, bland-CHO, tasty-CHO. Normal-weight, nondieting young adults consumed each of the meals for breakfast on separate days. The main finding was that tasty versions of high-FAT and high-CHO meals were more satiating than nutritionally identical bland meals, as indicated by a greater decrease in hunger ratings following the tasty meals. Changes in blood glucose and FFA were related to meal nutrient composition, but not to meal sensory properties. High-CHO meals tended to be more satiating than high-FAT meals. Consumption of each of the meals produced a similar decrease in pleasantness ratings of food-related tastes. Intake of carbohydrates was significantly higher at a self-selected lunch 5.25 h following a tasty breakfast. These findings indicate that hunger is decreased to a greater extent by meals flavored with aspartame and vanilla relative to nutritionally identical, unflavored meals. The satiety-enhancing effect of oral stimulation was found for both high-FAT and high-CHO meals.

Adult↗
PubMed1993

Integration of oral habituation and gastric signals in decerebrate rat pups.

During a series of oral infusions of a sweet solution, the ingestive responses of young rat pups habituate; pups stop responding to the infusions even when their stomachs are empty and the infused diet is nonnutritive. The rate of this oral habituation is enhanced by the addition of gastric fill signals, even in decerebrate pups. In intact but not in decerebrate pups, prior deprivation gates out the influence of gastric fill on habituation. This oral habituation system, responsive to multiple ingestion-related signals, may serve as the elemental process that integrates physiological state with ongoing behavior to control ingestion.

Animal Feed↗
PubMed1992

Oral habituation in rat pups is in the brainstem.

We have previously demonstrated a decremental, oral, experienced-based control of ingestion in rat pups that is potent, diet-specific, and long lasting. This control of ingestion is revealed in the decreases in mouthing responses of rat pups to repeated oral stimulation, a phenomenon that is well described as oral habituation. The present study examined the neural basis for oral habituation by examining the responses of decerebrate 10-day-old rat pups to repeated, brief infusions of a sucrose solution. Like neurologically intact pups, decerebrate pups showed distinct decreases in mouthing responses following a series of oral infusions. Thus, oral habituation is present in the hindbrain. Although intact pups demonstrated sensitization by showing increased responding to the first few stimulus presentations, decerebrates failed to show a sensitization to the stimulation. These results suggest that while the brainstem alone is sufficient for the expression of oral habituation, the forebrain also influences oral responsivity in intact animals.

Aging↗
PubMed1992

Ontogeny of feeding motor patterns in infant rats: an electromyographic analysis of suckling and chewing.

During mammalian ontogeny, there is a transition from suckling to the chewing of food. The question was asked: Is suckling a neuromuscular precursor to chewing, or are suckling and chewing independent systems? Electromyograms (EMGs) were recorded in rat pups of ages 6, 9, 12, 15, 18, and 21 days from the superficial masseter, anterior digastric, sternohyoideus, and genioglossus muscles during suckling and chewing. The EMG patterns of the 3 components of suckling behavior (nipple attachment, rhythmic sucking and the stretch response) are distinctive from one another and reflect the musculoskeletal biomechanics of suckling. Chewing EMGs are present by 12 days of age and attain the adult pattern by 18-21 days of age. During nipple attachment, pups exhibit a motor pattern that is similar to that of adult chewing, but other aspects of suckling differ from chewing in some EMG features. Comparison of EMGs between behaviors and between ages allowed interpretation of the degree of contunity of muscular activity across the suckling-to-chewing transition.

Aging↗
PubMed1992

Control of ingestion by oral habituation in rat pups.

The role of habituation of mouthing activity in the control of ingestion was investigated in 6-, 12-, and 18-day-old rat pups. In pups at all ages, oral habituation to a flavored diet inhibited ingestion of a continuous oral infusion of that same diet. Twelve-day-old pups that had orally habituated to a diet continued to consume less of a continuous oral infusion of that diet both 30 min and 3 hr later, and the duration of suppressed ingestion was shown to be dependent on the rate of stimulus presentation during habituation experience. These data suggest that oral habituation may be a diet-specific influence on both intra- and intermeal patterning.

Animals↗
PubMed1991

The early presence of food-oriented appetitive behavior in developing rats.

The appetitive behavior of 3- to 6-day-old rat pups was studied by testing their ability to direct their ingestive behavior to a restricted food source. We found that, from 3 days of age, pups were able to feed efficiently from such a source. More specifically, pups that were deprived of nutrition but not of maternal care as well as pups that were dehydrated ingested significantly more than nondeprived animals, and did so whether liquid diet was spread over the entire floor surface beneath them or restricted to a fraction of the floor surface. However, pups that had been nutritionally and maternally deprived were not able to direct their feeding. The general locomotor activation of pups in this latter group appeared to interfere with their ability to direct their behavior to the restricted source. These results indicate that from early ages, developing rats possess the appetitive competence to guide their behavior and suggest that previous findings of poorly directed behavior were a confound of the behavioral activation shown by pups tested in a state of maternal deprivation.

Animals↗
PubMed1991

Effects of hydrational state on ingestion in infant rats: is dehydration the only ingestive stimulus?

The physiological stimulus for deprivation-enhanced ingestion was studied in developing rats. During an overnight deprivation period, continuous gastric infusions of isotonic saline or milk were made to 6- and 15-day-old rat pups in order to preferentially maintain hydrational or hydrational and nutritional status, respectively. Pups' ingestion was then studied in oral-infusion tests. In 6-day-old pups that received either milk or saline infusions, ingestion was depressed relative to intake in pups that were simply deprived. But in 15-day-old pups, only milk infusions reduced intake. These findings suggest that the increased ingestion stimulated by deprivation in pups less than a week of age results primarily from dehydration, and thus that nutrient-related feeding does not emerge until later in development.

Animals↗
PubMed1991

Analysis of 2-DG autoradiograms using image-averaging and image-differencing procedures for systems-level description of neurobehavioral function.

Computer assisted 2-deoxyglucose (2-DG) autoradiography has been used to provide functional maps of areas of altered neural activity related to changes in an animal's behavior or state. The standard procedure for comparison of autoradiograms between different treatment groups has been to take measurement samples from predefined neuroanatomical regions and to average these across brains to attain statistical sensitivity for detecting treatment effects. Unfortunately, when sampling is restricted to predefined areas, important topographic information is lost along with the ability to reveal an unexpected change in neural activity. To preserve the rich topographical detail of metabolic information and to enhance the capacity to uncover novel areas of altered metabolic activity, we have developed a system for averaging entire images from 2-DG autoradiograms and for comparing the average images from two experimental groups by creating an image of differences. This procedure does not rely on sampling only preselected regions, but still allows statistical comparisons between experimental groups. The procedures we describe can be readily and inexpensively adapted for use in individual laboratories and are based on modifications of preexisting image analysis software. We show that, when average and difference images are created using standardized protocols for sectioning brain tissue and editing section images, they are impressively resolved and realistic and can serve as effective topographic descriptions of group differences in neural activity of functional and behavioral relevance.

Animals↗