Biomedical subjects

L D Abraham

Publications and source records attributed to L D Abraham.

25 records · Page 2Linked to original sources

PubMed1985

The distal hindlimb musculature of the cat. Patterns of normal use.

Chronic recordings were made of electromyographic (EMG) activity, tension, and length of distal hindlimb muscles in six cats performing a variety of normal motor tasks. Muscles studied thoroughly or in part were medial gastrocnemius, lateral gastrocnemius, plantaris, soleus, flexor digitorum brevis, flexor digitorum longus, flexor hallucis longus, tibialis posterior, tibialis anterior, extensor digitorum longus, peroneus longus, and peroneus brevis. Postural and locomotor activities were examined, as well as jumping, landing, scratching, and paw shaking. In general, muscles could be assigned to traditional groupings (e.g. extensor, flexor) related to the demands of the motor task. Patterns of muscle activity were most often consistent with current understanding of muscle mechanics and neural coordination. However, purely functional distinctions between flexor digitorum longus and flexor hallucis longus ("anatomical synergists") were made on the basis of activity patterns. Likewise, the activity of plantaris and flexor digitorum brevis, which are attached in series, was differentiated in certain tasks. The rhythmical oscillatory patterns of scratching and paw shaking were found to differ temporally in a manner consistent with the limb mechanics. In several cases, mechanical explanations of specific muscle activity required length and force records, as well as EMG patterns. Future efforts to study motor patterns should incorporate information about the relationships between muscle activation, tension, length and velocity.

Animals↗

PubMed1982

The interaction of endurance running and ethanol on skeletal muscle mitochondria.

This study was designed to measure the interaction of 8 weeks of endurance running and chronic ethanol consumption upon skeletal muscle mitochondria. Male Sprague-Dawley rats were assigned to 1 of 4 groups; ethanol diet sedentary (SED-E), ethanol diet trained (RUN-E), control diet sedentary (SED-E), and control diet trained (RUN-C). The ethanol groups, SED-E and RUN-E, consumed 35% of their calories as ethanol in a liquid diet. The trained groups, RUN-C and RUN-E, ran 5 days/wk for 8 weeks and were running 30 m/min for 90 min/day by the last week. The SED-E group had significantly lower body weights and gastrocnemius-plantaris weights than did the other 3 groups. The left ventricular heart weights showed no treatment effects. Mitochondrial respirations and cytochrome content were significantly depressed in the SED-E group and significantly elevated in the RUN-C and RUN-E groups. Two conclusions can be drawn from these data; (1) the ethanol diet caused a depression in mitochrondrial function of skeletal muscle, in weight gain, and in gastrocnemius-plantaris muscle mass amd (2) an endurance running program offset the deleterious effects of ethanol in all of these areas.

Alcoholism↗

PubMed1981

Effects of chlorpromazine on escape and avoidance responses: a closer look.

While a wealth of evidence has implicated the nigrostriatal dopamine system in the initiation of movement, most or all of these movements have been in a conditioned avoidance framework, and on the order of 3-14 seconds in latency. It is proposed here that an elucidation of dopaminergic involvement in movement initiation requires a behavioral paradigm wherein experimental animals must rapidly and voluntarily respond to a stimulus to move (i.e., in less than 300 msec, paralleling human reaction time). Such a paradigm was developed and implemented in a re-analysis of earlier reports of chlorpromazine (CPZ) effects on escape from an avoidance of electric shock. Catecholaminergic or dopaminergic receptor blocking by CPZ resulted in clear impairment of the ability to initiate rapid avoidance movements, but in contrast to earlier work, some impairment of escape responses was also seen. Results are seen as further support for dopaminergic involvement in the initiation of voluntary movement.

Animals↗

PubMed1980

Strain differences in dopamine receptor function and the initiation of movement.

The relationship between voluntary movement initiation (VMI) and caudate nucleus dopamine receptor dynamics was analyzed in two rat strains. Charles River CD/F F-344 (CR-CD/F) and Zivic-Miller CD (ZM-CD) rats (male, 125-150 g) were trained to rapidly release and reset a response lever to avoid electric shock. Whereas 86% of all CR-CD/Fs completed training, only 43% of the ZM-CDs were able to do so. Of those rats completing training, the CR-CD/Fs showed marginally higher avoidance percentage and significantly faster VMI latencies. Physiologically, the more behaviorally-successful CR-CD/Fs showed significantly higher affinity for binding than the trained ZM-CDs and the large group of ZM-CDs which could not be successfully trained. In contrast, the trained ZM-CDs showed significantly higher density of dopamine receptors Bmax than the ZM-CDs which failed to train and the trained CR-CD/Fs. The behavior-physiology continuum is summarized as follows: CR-CD/F Rats = highest affinity and lowest Bmax--rapid, highest percentage avoidance; Trained ZM-CD Rats = lowest affinity and highest Bmax--slower, high percentage avoidance; ZM-CD rats that failed training = intermediate affinity and Bmax--avoidance failure.

Animals↗

PubMed1979

Vestibular, auditory, and somatic input to the posterior thalamus of the cat.

The responses of 157 neural units in the magnocellular (mc) and parvocellular (pc) components of the medial geniculate nucleus (MG) and other nuclei of the posterior (PO) thalamic group were recorded and analyzed. Units were tested for a response to electrical stimulation of the vestibular nerve, natural auditory and electrical cochlear nerve stimulation, and natural stimulation of joint, muscle, and cutaneous receptors of the limbs, trunk, and neck (somatic stimulation). Only 45% of the units responded to these stimuli. Twenty-four percent of the responsive units were multimodal, responding to more than one stimulus. All multimodal units were activated by auditory stimuli. More units responding to vestibular stimulation were found in mcMG than in pcMG or other components of the PO group. Potentials evoked by vestibular nerve stimulation were recorded in all 3 regions with latencies of 5--25 msec. No evidence was found for a thalamic relay from vestibular nerve to cortex in the area investigated, since the recorded latency for activity from vestibular nerve stimulation was longer than the latency of responses recorded in the cortex. This region of the thalamus appears to be important for reception of auditory information and integration with vestibular and somatic modalities.

Acoustic Stimulation↗

PubMedDate not supplied

Post-contraction variations in motor pool excitability.

Previous evidence has shown a marked increase in motoneuronal excitability during muscle contraction and decreased post-contraction excitability. This post-contraction inhibition has been shown to persist up to 800 msec following the end of contraction (Gottlieb and Agarwal, 1973) and apparently continues with gradual recovery up to one minute (Enoka, Hutton and Eldred, 1980). These effects have been attributed in part to influences of muscle receptors on the homonymous motor pool. The purpose of the present study was to observe the time course of short term post-contraction effects, following a maximum isometric contraction, on excitability of the homonymous motoneuronal pool as measured by the Hoffmann reflex. Each of five subjects lay supine on a table with shoulder blocks to prevent movement during resisted plantar flexion. The subject's preferred foot was placed in a stirrup attached to a force gauge which measured tension. Recording electrodes were applied over the soleus muscle, and M- and H-responses were evoked by percutaneous electrical stimulation of the tibial nerve at the popliteal fossa. The stimulus strength was set to elicit a control H-reflex at rest of half the magnitude of the maximum H-reflex value. For each trial the subject performed a 6 s maximum contraction of the triceps surae muscle group, beginning on one visual signal and ending on a second visual signal. The H-reflex was elicited at semi-random intervals prior to and after the visual signal to relax. Increased H-reflex excitability was observed during muscle contraction followed by a marked decrease in evoked amplitudes with gradual recovery following the end of contraction.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMedDate not supplied

M-wave stability in H-reflex testing: analysis of three rejection criteria.

Two criteria reported in recent literature were compared with the criterion of 95% probability (using analysis of variance) for their abilities to detect significant differences in M-waves due to repositioning of the ankle joint during human soleus H-reflex testing. Data from five normal adult males were analyzed using all three rejection criteria, and results from the three analyses were compared. Variability of M-wave amplitudes within a condition was found to be quite small. Commonly used M-wave rejection criteria which do not account for within-condition variability of M-waves were shown to do a relatively poor job of detecting alterations of M-wave amplitude due to a change in ankle position.

Adult↗