Ultrastructure of the murine ascites tumor L4946. ANL-7409.
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Animals↗
Biomedical subjects
G B Jacobs
Publications and source records attributed to G B Jacobs.
Fine control of reinnervated muscle. Dynamic rehabilitation of facial paralysis.
Satisfactory rehabilitation of the paralyzed face has yet to be achieved. Ideally, both mobility and symmetry should be restored. In five rabbits, motion signals were picked up from the intact side by miniature strain gauges and channeled by means of an electronic circuit to electrodes placed around nerve pedicles previously implanted into the paralyzed side. An analog current produced in response to muscular contraction (afferent limb) resulted in graded and sustained contraction of the reinnervated side (efferent limb). In six animals, the tension of reinnervated strap muscles could be adjusted by varying the pulse width (0.1-10 msec) of a constant (0.5 mA) current applied to the nerve pedicles. Contraction (strain-gauge compression) of the intact face was followed by reciprocal graded relaxation of the reinnervated straps. Conversely, facial relaxation (elongation) induced graded strap contraction. An agonist-antagonist relationship was, thus, created between the two effectors. This approach may allow the paralyzed face to be electrically reanimated from the intact side in a symmetrical fashion closer to the physiologic state.
Afferent Pathways↗
New crisscross-shaped port design for universal serial pumps.
The long range goal is the development of a clinically useful, implantable, skeletal muscle powered cardiac assist device (MCAD). To accomplish this goal, two criteria must be met: good anatomic fit, and antithrombogenicity. Because of the relative locations of the latissimus dorsi (LD) muscle and aorta, there are two possible port arrangements: "crisscrossed" (C design), in which the ports are crossed to anastomotic sites, and "prong" shaped (P design), in which no crossover takes place. The purpose of this paper is to determine which of these designs is best from a fluid dynamic perspective, and hence has the best possibility for low thrombogenicity. Flow visualization (FV) techniques were used during two pumping conditions in a mock loop: worst case (MCAD off) and best case (MCAD driven optimally). Results of the MCAD off tests showed that both designs required immediate actuation (for example, an IABP console). However, FV studies under optimal conditions indicated superiority of the C design, most likely due to kinetic energy-induced rotary motion combined with a minimal interport distance. It is concluded that the C design provides ideal flow dynamics, even in valveless pumps, and also has application to valved devices.
Counterpulsation↗
Selective feedback control of spastic musculature in a canine model.
Muscular spasm, the etiology of which remains elusive, has been difficult to control. The authors, therefore, proposed selective restraint of forced contractions by a closed-loop circuit. In four dogs, the strap (n = 6) and thyroarytenoid (n = 4) muscles were submitted to tetanic contractions via bipolar supramaximal stimulation (30 Hz, 6 mA, 0.5 msec) of ansa hypoglossi and recurrent laryngeal nerves, respectively. Subsequent reduction of distance between two sonomicrometer crystals embedded into muscle was used in lieu of "spastic information" for a stimulator to deliver blocking signals through tripolar electrodes passed downstream. By modifying frequency (30-110 Hz) and current (60-95%) distribution between the central cathode and the peripheral anodes, significant relaxation (up to 100%) was recorded within "blocking windows," varying with each nerve (3-18 mA sweeps). The selective restraint of unwanted contractions, leaving "normal" subthreshold tone undisturbed, may offer a more mature approach to spastic disorders than destructive procedures, such as nerve section and its chemical counterpart, botulinum toxin injection.
Action Potentials↗
Is it possible to perform immediate cardiac assist using untrained latissimus dorsi muscle in a work-rest regimen?
The authors investigated what contractile force (CF) could be obtained from unconditioned latissimus dorsi muscle immediately after mobilization and for the 2 week vascular period of recovery. Latissimus dorsi muscle mobilization was performed on seven adult (4 experimental and 3 control) sheep leaving only the pedicle and the peripheral muscle intact. Telectronics stimulators (Myostim 7220; Teletronics Pacing Systems, Inc, Englewood, CO) were implanted. Immediately after mobilization 11-35% of the initial CF was lost. A 30 min fatigue test was performed 1 hr after mobilization (20 g/kg preload, 10 V, 10 Hz, 15 BPM, 6 impulses per burst) using a 1 min work-1 min rest regimen. Two sheep lost 2-12% of initial CF; two increased CF by 14-24%. At the end of the fatigue test, CF consisted of 74-89% of immobilized CF. Electrical stimulation training of the muscle was then initiated with the following regimen in the experimental animals only: 15 BPM, single impulses, 5 V, 10 Hz. Every day the muscle was exercised using a work-rest regimen to mimic cardiac assist, starting with 20 min on day 2, and increasing by 2 min per day until a total of 50 min was reached on day 16. All animals were retested for CF using a 42 min fatigue test on days 6, 11, and 16. On day 6, there was no fatigue evident in the experimental group during the 42 min test. CF after testing was 59-81% (mean 67%) of initial data. In the control group (animals with no electrical stimulation training protocol), CF decreased by 11% (from 64 to 53%). On day 11, there was no fatigue evident in the experimental group; CF in all animals increased by 2-8%. On day 16, there was also no fatigue evident in the experimental group; CF increased by 0-9%. An additional 20 min of continuous contraction (15 BPM) fatigue testing was performed on the muscle without rest between the tests. No fatigue was evident at the end of testing. Light microscopic analysis of latissimus dorsi muscle biopsy specimens taken on the days of testing showed no evidence of necrotic damage. Our investigations suggest that it may be possible to start muscle transformation immediately after mobilization and use the untrained latissimus dorsi muscle for cardiac assist immediately after surgery for short periods.
Animals↗
Force enhancement of skeletal muscle used for dynamic cardiomyoplasty and as a skeletal muscle ventricle.
Some patients with pre end-stage congestive heart disease do not receive a significant hemodynamic benefit from dynamic cardiomyoplasty because, during prolonged preoperative immobilization, their latissimus dorsi muscle (LDM) becomes extremely weak. It is the authors' hypothesis that the local administration of an anabolic steroid into an electrically stimulated LDM will produce a thicker and stronger muscle with significant resistance to fatigue. The electrical stimulation training protocol of sheep continued for 8 weeks. For localized anabolic steroid administration an osmotic pump was placed in a subcutaneous pocket and the catheter was introduced into the LDM. The contractile force of electrically stimulated and unstimulated control muscle was studied. Control data were calculated as 100% and all other data were corrected to control. After 4 weeks there was no decrease in contractile force. The change seen was from 88 to 100% with different preloads (10, 15, and 20 g/kg) and amplitudes of impulses (5 and 10 V). After 8 weeks, the LDM was more powerful than before electrical stimulation, with a change of 97-133%. Usually after 8 weeks of electrical stimulation alone, contractile force decreases to 70-75%. During a fatigue test (30 min, 100 bursts per minute, 10-25 Hz, ripple frequency, 10 V impulse amplitude) after 4 and 8 weeks of our protocol, the LDM lost only 12% of its initial force, whereas control muscle lost 40%. Thus local anabolic steroid administration makes the LDM stronger and more useful for cardiomyoplasty.
Animals↗
Optimization of pacing parameters for conditioned latissimus dorsi muscle in cardiomyoplasty.
Synchronous paced contractions of latissimus dorsi muscle pedicle (LDM) around the heart improve ventricular function in dynamic cardiomyoplasty. To optimize assistance and prolong pacemaker battery life, the LDM should be stimulated with the lowest energy pacing parameters (PP) that will produce maximal muscle contraction. Muscle fractional shortening (FS) and duration of contraction (CT) were studied in conditioned, fatigue-resistant LDM of six goats. Fractional shortening and CT were determined at increasing amplitude, (A, 1-6v); pulse width, (PW, 60-450 musec); and frequency, (F, 5-130 Hz). Maximal rate of contraction was determined by pacing at higher rates. Maximal FS plateaued after V, 2.4 +/- .6v; PW, 125 +/- 47 musec; and F, 36 +/- 9 Hz. Mean CT for all PP was significantly longer (p less than or equal to 0.001) than the burst length (185 msec). Increasing F resulted in CT, which peaked at 460 +/- 59 msec. Increasing rate of contraction demonstrated that over 87 beats per minute the muscle fails to achieve complete relaxation, and, therefore, maximal FS.
Animals↗
Electronic pacing of incapacitated head and neck structures.
Paralysis in the head and neck can affect any motor or mixed cranial nerves and the cervical roots. Most conspicuous deficits, however, involve the larynx and the face. The capacity for denervated striated muscle to undergo reinnervation, and the presence of remaining sources of information, have allowed coordinated rehabilitation of incapacitated cervical neuromuscular systems. The object of further related research should focus on the long-term efficacy of the reinnervated muscle machinery and the potential complexities of electronic integration.
Animals↗
Effect of a pulsing electromagnetic field on metabolically derived osteoporosis in rats: a pilot study.
The literature suggests that a pulsating electromagnetic field (PEMF) is effective against bone loss in disuse osteoporosis. This study was conducted to evaluate the effects of PEMF on metabolically derived osteoporosis in rats. Sixteen 5 month old female Sprague-Dawley rats were divided into three groups (G-1,2,3). G-1 was given a normal diet and no exposure to PEMF; G-2,3 were oophrectomized and fed a low calcium diet for 8 months; and G-3 was also exposed for 24 hr/day to PEMF generated by applying a 15 Hz, 5.6 A peak to peak square wave to Helmholtz coils (64 cm I.D., 200 turns/coil). The rats were sacrificed at 4, 6, and 8 months. Skeletal changes were analyzed by measurements of acid extracted bone calcium and bone mineral content (BMC) using single photon absorptiometry (SPA). Although all animals started at approximately the same weight (mean of 290.0 g), G-2 showed a more progressive increase. While the mean weight after 8 months in G-1 was 350.0 g, and 352.5 g for G-3, that in G-2 was 400.0 g. The calcium content of the femur in G-2 and G-3 at 8 months was lower than that of G-1, but there were no significant differences among the three groups.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
New horizons in dynamic rehabilitation of paralyzed laryngeal functions.
Bilateral vocal cord paralysis can result in inspiratory difficulty, while stroke can impair swallowing and be followed by severe aspiration. Ideally, these mutually exclusive functions must be rehabilitated dynamically. The principle of the artificial reflex arc (ARA) entails appropriate pick-up information, which is then sent to a modulator that in turn synchronously stimulates the impaired effector. In vocal cord paralysis (six dogs), respiratory information has been picked up via tracheal strain gauges and transthoracic impedance electrodes, producing an analog voltage proportional to respective changes during inspiration. A trigger and a stimulator circuit were used to drive an electrode placed around a nerve-muscle pedicle previously implanted into the posterior cricoarytenoid muscle. Two msec square waves with 1.8 V amplitude and 50 Hz frequency resulted in frank vocal cord abduction synchronous with inspiratory flow. Conversely, vocal fold closure can be paced from information originating from strain gauges placed on the hypopharynx (four dogs). Stretch stimulating deglutition resulted in controlled output of a constant current stimulator driving an electrode passed around both recurrent laryngeal nerves. An adjustable stimulus from 0 to 20 mA at 25 Hz produced tetanic closure of the vocal folds. This might offer promise for electronic control of the transplanted larynx.
Animals↗
Mode comparison study for a completely implantable TAH (CITAH) system.
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Animals↗
Biolized intrathoracic left ventricular assist device (LVAD).
The design of an intrathoracic left ventricular assist device (LVAD) is briefly described. The unique feature of the LVAD is that all blood-contacting surfaces are biolized, having either chemically treated natural tissues or protein coatings. The blood-contacting surface of the housing is glutaraldehyde-treated pericardium and is covered with natural rubber and polyurethane. Tri-leaflet valves fabricated from human dura mater are used at the pump inlet; glutaraldehyde-treated bovine aortic valves are used at the outlet. The pumping diaphragm, made of polyolefin rubber with a textured surface, is coated with gelatin and treated with glutaraldehyde. Anticoagulants are not used with this device. Extensive in vivo and in vitro testing in the development of the pumps led to the current configuration having good performance, long life, and improved blood compatibility.
Animals↗
Aseptic meningitis and pseudomeningocele formation as a complication of surgery in the posterior fossa.
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Adolescent↗