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Biomedical subjects

A J Nitz

Publications and source records attributed to A J Nitz.

25 records · Page 2Linked to original sources
PubMed1986

Effects of short-term electrical stimulation on the ultrastructure of rat skeletal muscles.

The purpose of this study was to determine the effects of short-term, 2,500-Hz carrier-wave frequency electrical stimulation on the ultrastructure of fast-twitch rat skeletal muscles. Thirteen Sprague-Dawley male rats were divided into three groups: daily treatment (Group 1), every-other-day treatment (Group 2), and control (Group 3). The medial quadriceps femoris and hamstring (semitendinosus and semimembranosus) muscles of the right thigh were treated with short-term electrical stimulation. After treatment, the animals were sacrificed, and their treated and sham quadriceps femoris and hamstring muscles were removed, fixed by immersion, and processed for electron microscopy. Morphometric measurements were made on electron micrographs using a Videoplan computer system, and the results were analyzed statistically. The results revealed that mitochondria, triads, and glycogen content of the fast-twitch muscles changed to resemble those of slow-twitch muscles. In view of these results, clinicians should consider the possibility that similar changes also might occur in human subjects under clinical conditions.

Animals↗
PubMed1986

Comparison of muscle spindle concentrations in large and small human epaxial muscles acting in parallel combinations.

A small short muscle acting across a joint in parallel with vastly larger and longer muscles is clearly unable to play more than a minimal mechanical role in such a "parallel muscle combination" (PMC). This research investigates a feed back role for the small muscles of PMCs, proposing a significantly higher muscle spindle concentration therein to be consistent with this role. Epaxial PMCs (semispinalis and multifidus versus rotatores brevis) from the C5-C6, T6-T7, and L4-L5 regions of three 36-week-old male fetuses and two adult cadavers were removed and fixed in Carnoy's fluid. Tissue samples were embedded in paraffin, cut into 10 microns thick sections perpendicular to the muscle's longitudinal axis and stained by Harris' hematoxylin and eosin. Representative tissue sections were projected onto a sterological grid and the percentage volume of spindles determined. Data were analyzed with Student's unpaired t test. In all PMCs, rotators brevis spindle percentage volumes ranged from 4.58 to 7.30 times higher than those of multifidus and semispinalis. Differences in mean spindle percentage volumes between large and small members of all PMCs were significant (P less than .0001). Our findings are consistent with the notion of a "kinesiological monitor" or feedback role for rotatores brevis.

Adult↗
PubMed1982

Ultrastructural changes in rat peripheral nerve following pneumatic tourniquet compression.

The sciatic nerves of 12 male rats were examined in the electron microscope 14 days after pneumatic tourniquet compression. Tourniquet pressure was maintained at 300 mmHg for varied lengths of time (30 minutes to 3 hours). Nerves compressed for 30 minutes showed very mild fissuring of the myelin without axonal degeneration. Examination of nerves compressed for 1 to 3 hours showed progressively more varied and extensive damage. Changes included splaying of myelin lamellae, axonal shrinkage with periaxonal edema. Schwann cell hypertrophy, and an increase in the number of microtubules and mitochondria per unit area. The myelin sheaths of some fibers, compressed for more than 2 hours, were completely ruptured. These changes resemble nerve lesions which could be induced by a variety of experimental procedures. Ultrastructural changes produced by tourniquet compression are apparently time-related and affect large-diameter nerves more profoundly than smaller-diameter nerves. The data reported provide an explanation for delayed muscle rehabilitation experienced by patients who have undergone extremity surgery with pneumatic tourniquet application. The evidence presented suggests that the incidence of tourniquet palsy may be far greater than previously recognized.

Animals↗
PubMed1980

Oxygen consumption for lower extremity exercises in normal subjects and burned patients.

The purpose of this study was to compare the oxygen requirements for normal subjects and burned patients during rest and while performing two separate exercises of the quadriceps femoris muscles. The oxygen consumption of 10 normal subjects and 10 burned patients while at rest and while performing each exercise was measured. The resting and exercising oxygen-consumption levels for burned patients were significantly greater (p < .01) than for normal subjects. However, the mean difference in increased oxygen consumption during two exercises for normal subjects and for burned patients was not significant (p > .05). The elevated resting and exercising oxygen-consumption levels in burned patients were considered to be related to the hypermetabolic response characteristic of thermally injured patients.

Adolescent↗
PubMedDate not supplied

Postmeniscectomy tourniquet palsy and functional sequelae.

A pattern of variability was noted in the rehabilitative progress of patients undergoing knee surgery. Forty-eight patients who underwent routine medial or lateral meniscectomy were studied in a controlled, randomized, prospective investigation designed to identify electromyographic (EMG) and functional deficits associated with using a pneumatic tourniquet in knee surgery. The control group (24 individuals) underwent knee surgery without te use of a tourniquet. Six weeks postoperatively all patients were studied by EMG and functionally by determining the single leg vertical leap of the affected leg and expressing this as a percentage of that accomplished by th sound leg. The results were: (1) 17 of 24 (71%) of the tourniquet group had EMG evidence of denervation and a functional capacity of 39% of the normal leg. (2) 7 of 24 (29%) of the tourniquet group had no evidence of denervation and a 71% functional capacity. (3) The control group had no evidence of denervation and a functional capacity of 79%. Of the patients on whom a tourniquet was used, total tourniquet time and pressure did not vary significantly between those patients who demonstrated EMG findings and those who did not. Arthrotomy in the absence of a tourniquet required more attention to hemostasis, but did not present overwhelming difficulty. Operative time was slightly prolonged. This investigation suggests that the ideal of early return to functional activity after knee surgery can best be accomplished by avoiding use of a pneumatic tourniquet.

Adolescent↗
PubMedDate not supplied

Nerve injury and grades II and III ankle sprains.

Nerve injuries associated with inversion sprains of the ankle have been mentioned in the literature on a case presentation basis only. Sixty-six consecutive patients with Grade II (30) and Grade III (36) ankle sprains were examined by electromyography 2 weeks after injury to determine the presence and distribution of nerve injuries. Ankle active range of motion (AROM) and the number of weeks postinjury when the patient could heel/toe walk and return to full activity were also noted. Five patients (17%) with Grade II sprains had mild peroneal nerve injury and three (10%) injured the tibial nerve. Clinical measurements were normal by the end of the second week. Thirty-one patients (86%) with Grade III sprains injured their peroneal nerve, while 30 (83%) incurred posterior tibial nerve injury. Ankle AROM was impaired, and heel/toe walking (5.1 weeks) and return to full activity (5.3 weeks) were markedly prolonged. The likely cause of this injury is considered to be a mild nerve traction or a hematoma in the epineural sheath at the bifurcation of the sciatic nerve into peroneal and posterior tibial branches. This report indicates that a consistently high percentage of patients with Grade III ankle sprains sustain a significant injury to both motor nerves in the leg and that rehabilitation time is markedly prolonged.

Adult↗