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Biomedical subjects

G B Jacobs

Publications and source records attributed to G B Jacobs.

At least 37 records · Page 2Linked to original sources
PubMed1989

An artificial myotatic reflex: a potential avenue to fine motor control.

When a striated muscle becomes paralyzed, not only its motor function, but its sensory innervation may be impaired. Methods of rehabilitation have previously focused only on motor innervation, although striated muscles are submitted to self-regulation of length and tension. Indeed, reinnervated muscle may not contract appropriately unless sensory information is available, nor is it known whether sensory receptors are included in the reinnervation process. We hypothesized that the myotatic reflex (MR) would be absent in the event these sensory organs are not reinnervated, and that an artificial myotatic reflex (AMR) would be useful in reestablishing fine motor control. The strap muscles were exposed in six anesthetized rabbits. The MR was verified by stretching an intact sternohyoid muscle. Next, loss of the reflex was documented after the ipsilateral ansa hypoglossi was divided, and a crossover nerve-muscle pedicle (NMP) was brought in from the opposite sternothyroid. After 3 months, the MR was still absent; however, stretch of the contralateral sternohyoid produced a reflex response on the reinnervated side. A strain gauge sutured to the reinnervated muscle was linked to an electronic modulator so that stretch induced electric stimulation of the NMP and contraction (the AMR). We conclude that (1) proprioception is not reestablished in the reinnervated muscle; (2) by contrast, sensory information from the muscle of origin of the NMP is conveyed to the reinnervated side; and (3) the AMR offers promise toward more sophisticated control of paralyzed (i.e., facial, laryngeal) musculature.

Animals↗
PubMed1989

Artificial agonist/antagonist coupling in paralyzed muscles: electronic balance of reinnervated straps from facial activity in the rabbit.

Normal striated muscular contraction such as occurs in the face is the result of finely balanced activities monitored by the central nervous system. Previous approaches to rehabilitation have been limited to restoring only motor function, ignoring the proprioceptive input that normally originates at the level of each muscle. In this pilot study, proprioceptive information originating in facial muscles (considered as agonists) is artificially channeled to nerve pedicles, reinnervating straps in the rabbit to produce antagonist action. Further development of this concept can lead to finer control of reinnervated muscles of the face or elsewhere.

Animals↗
PubMed1988

The E4T electric powered total artificial heart (TAH).

The E4T is a totally implantable total artificial heart (TAH) resulting from many years of research work at the Cleveland Clinic Foundation (CCF) and Nimbus, Inc. It consists of four implanted subsystems: the pumping unit, the variable volume device, the transcutaneous transformer, and the internal battery. The pumping unit consists of two CCF biolized pusher plate pumps, and a Nimbus electrohydraulic energy converter. The control logic is based on a left master, alternating beating scheme. The timing difference between end right eject and end left fill determines the actuator speed adjustment. The pumps free fill, so left-right flow differences are easily accommodated. A prototype system has been built and begun testing to validate and refine the design details.

Electric Power Supplies↗
PubMed1988

Artificial reflex arc: a potential solution for chronic aspiration. II. A canine study based on a laryngeal prosthesis.

Long-term and repeated aspiration can result in pneumonia and eventually death. To avoid current techniques which divert or close off the incompetent larynx, the authors have recently described an artificial reflex arc (ARA), in hopes of providing a dynamic solution to this problem. With this concept, a segment of skin surface with intact sensory innervation is implanted into the pharynx in the path of the food bolus. Resulting neural impulses would be detected by a perineural electrode and then channeled to both recurrent laryngeal nerves via an electronic pacemaker to cause vocal fold adduction at the critical time during swallowing. A pilot study using a tubed cervical cutaneous surface has yielded promising results in the canine. In this current study, an alternate means for information pickup based upon use of a miniature strain gage is presented. Mechanical stimulation of the hypopharynx using this "sensory" detector resulted in synchronous laryngeal adduction of the vocal folds, as documented graphically and on videotape.

Animals↗
PubMed1987

Dynamic rehabilitation of the paralyzed face: I. Electronic control of reinnervated muscles from intact facial musculature in the rabbit.

An entirely satisfactory solution to dynamic rehabilitation of the paralyzed facial musculature has not yet been found. Recent interest in selective reinnervation of the laryngeal musculature, synchronous with appropriate afferent information, has led us to propose that miniature strain gauges be placed on one or more muscles of facial expression on the intact side to channel electrical signals to the opposite corresponding facial musculature reinnervated via nerve-muscle pedicles. In order to avoid introducing extraneous factors related to facial motion, this principle was first studied on crossover ansa hypoglossi nerve-muscle pedicles in New Zealand white rabbits. Surgery was performed on a total of five animals that were under general anesthesia with xylazine and ketamine, through a midline neck incision. The animals were reexplored after 12 weeks, and after verification that reinnervation had taken place, a vertical incision was made under the external canthus, in order to expose the facial nerve. A miniature strain gauge was then sutured on the facial musculature and connected to a central modulating unit that was, in turn, linked to the nerve-muscle pedicle via a monopolar electrode. Facial wiggle that resulted from direct electrical facial nerve stimulation caused synchronous contraction of all reinnervated strap muscles under study; this was documented on film and through facial and strap muscle activity tracings. Our next step will be to extend this principle to paralyzed facial muscles. If successful, this system could be miniaturized for long-term implantation in human beings.

Animals↗
PubMed1985

Anatomical considerations in the design of a long-term implantable human left ventricle assist system.

A permanently implantable left ventricle assist system (LVAS) is being developed and is planned to be implanted in the left chest cavity against the chest wall with the electrohydraulic energy converter placed in a resected rib space. The inflow and outflow pump ports are connected to the left ventricle (LV) apex and to the descending aorta, respectively. Three additional major components of this system consist of the transcutaneous energy transmission system (TETS) (Thermedics), the variable volume device (VVD), and the internal battery. To finalize the design of this integrated system, key anatomical information was obtained by a special radiographic and angiographic study of 31 adult men with a varying degree of coronary artery disease and myocardial dysfunction. These data were combined with the previous computed tomography study by using a standard vertical reference system. The resultant integrated data, which consist of the three-dimensional chest model, the LV apex and axis orientation, rib orientation, chest wall thickness, and the descending aorta location, were used to define the design and anatomical locations of the inflow and outflow pump ports, the VVD, the pump and energy converter orientation, the TETS, and the internal battery. The most critical component for the design was found to be the inflow system. With regard to the average coronary disease patient, an anatomically practical configuration was demonstrated to exist for the presently proposed LVAS. Design flexibility was allowed for some of the critical components in order to fit the system in a large number of patients regardless of the stage and type of the underlying disease.

Adult↗
PubMed1984

Perilymphatic fistula--a definitive and curable cause of vertigo following head trauma.

Vertigo or disequilibrium occurring in patients after concussive and nonconcussive head trauma may be due to a pathologic perilymphatic fistula from the inner ear through the oval and round window areas of the middle ear. Of 33 patients who had successful grafting of the fistulous area at middle ear exploration, 32 had resolution of vertigo, and 12 of 23 who had an associated hearing loss had improved hearing. Perilymphatic fistulas associated with vertigo and hearing loss after head trauma can be diagnosed with great certainty and are surgically curable in the great majority of cases. Patients with post-concussive syndrome, whose symptoms include vertigo or disequilibrium, should have a thorough otologic evaluation for the possibility of a perilymphatic fistula.

Craniocerebral Trauma↗
PubMed1980

Bovine aortic and human dura mater valves: a comparative study in artificial hearts in calves.

Thirty-one glutaraldehyde-treated bovine aortic valves (BAVs) and 105 glycerol-treated human dura mater valves (HDVs) were used in 51 various artificial hearts up to 316 days in calves. Multiple valves were implanted in the same animal under different hemodynamic conditions. A comparative study of these valves was performed in terms of blood compatibility and durability with relation to the different hemodynamic environments. Both BAVs and HDVs showed good blood compatibility. The degradation of collagen bundles of the valves began as early as 7 days in BAVs and 13 days in HDVs, and was seen in the hinged portions of the cusps. The fiber separation and resultant void formation were followed with insudation of blood elements and subsequent calcification. Calcification was dystrophic in nature and was encountered in 70.9% of BAVs and 7.6% of HDVs. All 17 BAVs used more than 30 days were calcified; in HDVs the earliest calcified lesion was seen in a 78 day specimen. The pathological changes were more severe in the left side than the right of the total artificial hearts. These results clearly indicated that the HDV is more durable than the glutaraldehyde-treated BAV. It was suggested that degradation of these tissue valves is greatly affected by the degree of hemodynamic stress on the valve cusp. Although glutaraldehyde treatment has increased the durability of tissue valves in general, the structure of the valve tissue also plays an important role in long-term durability.

Animals↗
PubMed1979

Arteriovenous malformations of the spinal cord.

Spinal AVM's are not rare, and are diagnosed today with increasing frequency by utilization of moedern neuroradiological techniques. Their relationship to the spinal medulla is related to vascular embryological anatomy, and the only effective treatment is directed at obliteration of the fistula. Males are affected more frequently in the middle years of life. Symptoms may mimic spinal cord tumors and demyelinating disorders. The pathogenesis of symptoms, classification, and methods of diagnosis are reviewed, and the various methods of treatment discussed.

Arteriovenous Malformations↗
PubMed1978

Human thoracic anatomy relevant to implantable artificial hearts.

The objective of this study is to define the human thorax in a quantitative statistical manner such that the information will be useful to the designers of cardiac prostheses, both total replacement and assist devices. This paper pertains specifically to anatomical parameters relevant to the total artificial heart. Methods were developed for generating an integrated, statistical model of the anatomical structures within the human thorax. These methods involve definition of the anatomy in four areas: chest wall, pericardium, vascular connection locations, and great vessels. Results are presented in three dimensional scale views of the human thorax showing the main features pertinent to cardiac prosthesis implantation. Statistical variability of this data is also included. Measurements were obtained from a number of sources and represent both normal and diseased patients. The ERDA total artificial heart was shown to successfully fit the fiftieth percentile adult male human.

Aorta↗
PubMed1978

Cerebral death.

Explore the source record for details and available documents.

Brain Death↗
PubMed1977

Disc space infections in children.

Intractable low back pain in children is often due to disc space infections. The clinical presentation, diagnostic workup, and treatment of four cases are presented. Symptoms often occur well before radiographic findings are evident. The diagnosis can only be made by a high degree of suspicion and repeated X-rays. Antecedent causes, such as urinary infection or intravenous administration of narcotics were lacking in this group. Fever or a preceding febrile illness was often, but not invariably, present. Percutaneous biopsies were not usually helpful. Myelography in each instance was normal. Bed rest reduced but did not alleviate the back pain. The institution of appropriate antibiotic therapy resulted in a prompt diminution of pain.

Adolescent↗
PubMed1977

Survival for 145 days with a total artificial heart.

A calf into which a biolized, total artificial heart (TAH) had been implanted survived for 145 days. All measured physiological parameters except central venous pressure (CVP) were back to normal one month after implantation, and thereafter the animal's physiological development was similar to that of a normal calf. The intimal weight, which was 96 kilograms at implantation, reached 190 kilogram at the end of experiment, with a daily gain rate of 0.9 kilogram per day. After the nineteenth postoperative week, signs of congestive heart failure appeared, such as high venous pressure, ascites, and enlarged liver although the calf outwardly appeared well. On postoperative day 146, the animal started foaming at the mouth, and a convulsion occurred; then, the experiment was terminated after 3,494 hours of pumping. At autopsy, there were acute bilateral bronchopneumonia involving mostly both upper lobes, pulmonary edema, slight chronic pneumonitis, and hepatomegaly. There were no serious thrombotic deposits inside the cardiac prosthesis.

Animals↗