Biomedical subjects

D M Hendershot

Publications and source records attributed to D M Hendershot.

6 recordsLinked to original sources

PubMed2000

Effects of low doses of caffeine on aggressive behavior of male rats.

To date, the effect of low doses of caffeine on aggression has not been systematically examined. Doses of caffeine greater than 30 mg/kg appear to reduce social interaction and aggression in all species studied. In a double blind study of the effects of low doses of caffeine on aggression, rats were housed four per cage, and aggressive behavior against an intruder was recorded during baseline and following administration of 2.5, 5, 10, and 20 mg/kg caffeine. Aggressive behavior was significantly increased following administration of the higher doses of caffeine. Doses of 5, 10, and 20 mg/kg caffeine all were effective in increasing pushing behavior, whereas doses of 5 and 10 mg/kg were most effective in increasing boxing behavior, and a dose of 10 mg/kg was significantly more effective than other doses in increasing chasing and roll-tumble-bite behaviors. Based on these results and other published reports, the inverted-U shaped dose-dependent effect of caffeine on aggression appears to apply, with aggressive behavior being most elevated following doses of 5-20 mg/kg caffeine, less elevated following 2.5 mg/kg or 30 mg/kg, and significantly reduced with doses above 40 mg/kg and at doses below 2.5 mg/kg.

Aggression↗

PubMed1995

Walking when utilizing a sensory feedback system and an electrical muscle stimulation gait orthosis.

Electrical muscle stimulators (EMS) have been combined with a reciprocating gait orthosis (RGO) to produce an EMS-RGO system for constant velocity ambulation exercise in a spinal cord injured (SCI) individual. The objective of this study is to evaluate an auditory feedback system (AFS) used by the SCI subject when ambulating with the EMS-RGO. Three different types of auditory signals (M = metronome alone, MSL = metronome plus stride length information, and NONE = no auditory feedback) were examined at three different constant walking velocities (WV1 = 0.64 kph, WV2 = 1.22 kph, and WV3 = 1.80 kph). The experimental design was 3 x 3 full factorial with repeated measures, and the dependent variable was the absolute error (AE) of walking distance (absolute value of the distance the subject walked in one minute subtracted from the target distance). A block diagram and circuit schematic of the AFS is provided. The results indicate that at WV1 there is no significant difference of AE among the three auditory conditions (M, MSL and NONE). At WV2, the AE for the NONE auditory condition is significantly greater than the AE for M and MSL (p < 0.05). At WV3, the AE for the NONE auditory condition is significantly less than the AE for M and MSL (p < 0.05). Finally, there was no significant difference in AE between both the M and MSL auditory conditions at any of the three walking velocities. This study indicates that an adequate sensory feedback system for constant velocity control of ambulation in this SCI subject consists of metronome only auditory feedback.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1991

Walking while using a sensory tactile feedback system: potential use with a functional electrical stimulation orthosis.

A major limitation in the utilization of a functional electrical stimulation (FES) orthosis for routine, daily standing and walking of the spinal-cord-injured person is that visual monitoring is required to maintain balance and the walking pace. For standing and walking to be continuous and automatic with such an orthosis, a closed-loop sensory feedback system is proposed and evaluated; it provides vibrotactile feedback as a substitute to one's own visual sensation. Eight blindfolded experimental subjects were utilized as 'imitators' to interpret the footfalls of a second person (the pace setter). The experimental objective was to test the hypothesis that sufficient information could be transferred by way of the sensory (tactile) feedback system to the 'imitator' and to determine effectively foot position and anticipate the next step of the pacesetter. Quantitative analysis evaluated the effect of three different levels of training, under two different levels of cognitive load. The results disclosed a significant improvement in subject performance at the higher training levels compared with the 'no training' level (P = 0.01). Neither the cognitive load nor the interaction of training and cognitive load altered significantly the effect of training on subject performance. The experimental hypothesis is therefore satisfied that sufficient information was indeed transferred using the apparatus described. Such information (when utilized in conjunction with a thorough training programme) could be used in a practical sense by a paraplegic individual to interpret his own foot steps. Through continued use and training, it is likely that this information could become subconscious and automatic.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1991

Functional electrical stimulation and reciprocating gait orthosis for ambulation exercise in a tetraplegic patient: a case study.

The purpose of this paper is to report the cardiopulmonary stresses (as indicated by heart rate, blood pressure, oxygen consumption and task cost) for a tetraplegic individual when walking with electrical stimulation and a gait orthosis as opposed to walking with a gait orthosis alone. Functional electrical stimulation (FES), when interfaced with a reciprocating gait orthosis (RGO), resulted in walking exercise for a C-7 level tetraplegic subject, who was 8 years post-injury. Cardiopulmonary measurements were made and task costs calculated on this individual during progressive velocity walking with the FES-RGO and the orthosis alone (without FES). Results for the tetraplegic individual indicate that there were no significant changes in heart rate at the various walking velocities with respect to the two systems. However, systolic blood pressure was significantly reduced at the three highest walking velocities (1.2, 1.6 and 2.0 kph) when using the FES and orthosis system as compared to orthosis-alone walking (p less than .025, p less than .005 and p less than .025 respectively). Calculated oxygen consumption was significantly reduced and calculated task cost improved at the highest walking velocity (2.0 kph) when using the FES-RGO system as compared to using only the RGO (p less than .025). It is concluded that cardiopulmonary stresses are significantly less for this tetraplegic individual when ambulating at the higher velocities with electrical stimulation and a gait orthosis than when walking with a gait orthosis alone. This may result in improved endurance during each walking session and (consequently) an improved aerobic exercise effect. This might also allow some tetraplegics, who would be unable to walk with the RGO alone, to walk with electrical stimulation and the RGO.

Adult↗

PubMed1991

A systems approach to medically prescribed functional electrical stimulation. Ambulation after spinal cord injury.

A functional electrical stimulation (FES) system for ambulation of spinal cord injured patients has been described to consist of physician prescriptable, commercially available components. The system components are: electrical muscle stimulators, a reciprocating gait orthosis and the electrode delivery system. A systems approach to medically prescribed FES ambulation requires the interfacing of these basic components, each of which has the flexibility to adjust to the optimal configuration for each individual patient. The electrode delivery system is of central importance in interfacing the basic components. This report describes the electrode delivery system, a transcutaneous transducer garment, which allows a variety of electrode configurations and stimulation patterns. The system has been successfully employed on a C7 level tetraplegic patient and a T9 level paraplegic patient.

Adult↗

PubMed1984

The interrelationship between blood pressure, intramuscular pressure, and isometric endurance in fast and slow twitch skeletal muscle in the cat.

Two series of experiments were performed to examine the interrelationships between blood pressure, intramuscular pressure, muscle blood flow, and the endurance for isometric exercise in a fast (medial gastrocnemius) and a slow (soleus) twitch muscle of the cat. In the first series of experiments, the relationship between tension and intramuscular pressure was examined. It was found that intramuscular pressure was linearly related to tension in both muscles. However, at any proportion of the muscles maximum tension, the intramuscular pressure of the medial gastrocnemius muscle (the stronger of the muscles) was about twice that of the soleus. A second series of experiments was conducted in which blood pressure was increased above intramuscular pressure and the effect of blood pressure on isometric endurance was measured. The pressure of the perfusing blood of the cat's hind limb was adjusted to either 13.3, 26.6, or 39.9 kPa. It was found that increased perfusion of the muscle resulted in a dramatic increase in the endurance for contractions sustained at isometric tensions below 60% of the muscle's initial strength. In contrast, for contractions above this tension, the effect of increased perfusion was much less pronounced.

Animals↗