Morphometric analysis of rabbit skeletal muscle and peripheral nerve tissue after electrical stimulation.

Transcutaneous medium frequency electrical stimulation is used extensively to improve muscle strength in people who encounter difficulty in improving strength voluntarily. The purpose of this study was to describe some morphometric effects of electrical stimulation applied to rabbit skeletal muscle and peripheral nerve tissue (N = 5 control and 7 experimental rabbits). Intermittent electrical current (4000 Hz pulse modulated at 50 Hz) was applied transcutaneously to adult female rabbit thigh muscle 3 times/week for 3 months. Muscle ATPase histochemical staining, followed by morphometric analysis, demonstrated that type IIB fibers in stimulated muscles (sartorius and vastus lateralis) had larger cross-sectional areas in comparison to nonstimulated muscle fibers. Type IIA fibers of the stimulated sartorius muscle also were hypertrophied in comparison to nonstimulated muscle fibers. The percentage distribution of muscle fiber types did not change significantly as a result of stimulation. The femoral nerves of these rabbits were fixed and stained. Morphometric analysis did not detect any significant change in myelin cross-sectional area or thickness. Also, nerve axoplasmic cross-sectional area in stimulated femoral nerves was not significantly different from controls. These data suggest that electrical stimulation can increase the size of skeletal muscle fibers if applied consistently for an extended period of time. Further research is needed to further characterize this effect and to determine whether the same effect can be observed in humans after prolonged stimulation. J Orthop Sports Phys Ther 1990;11(7):313-320.

Reliability of quantitative muscle testing in healthy children and in children with Duchenne muscular dystrophy using a hand-held dynamometer.

The purpose of this study was to examine intratester and test-retest reliability using a hand-held dynamometer for the measurement of isometric muscle strength in 28 healthy children and children with Duchenne muscular dystrophy. The Dystrophic Group consisted of 14 children diagnosed with Duchenne muscular dystrophy, and the Healthy Group consisted of 14 age-matched children with no history of orthopedic or neuromuscular disorders. One physical therapist tested hip and knee extension, elbow flexion, and shoulder abduction in each child bilaterally. A two-way analysis of variance for repeated measures was used to analyze differences between measurements taken within and across the testing sessions. Pearson product-moment correlation coefficients were determined on mean values across the testing sessions for each variable. No significant differences (p greater than .05) between measurements taken within or across testing sessions were found in either the Dystrophic Group or the Healthy Group. Correlation coefficients for the Dystrophic Group ranged from .83 to .99 for the variables tested. Correlation coefficients for the Healthy Group ranged from .74 to .99. The results suggest that the hand-held dynamometer can be used as a reliable instrument in measuring the isometric strength of selected muscles in children.

The kinetic differences between sodium nitrite, amyl nitrite and nitroglycerin oxidation of hemoglobin.

The effect of sodium nitrite, amyl nitrite and nitroglycerin (glyceryl trinitrate) on the hemoglobin of adult erythrocytes was examined in vitro. Both amyl nitrite and nitroglycerin reacted immediately with oxyhemoglobin to effect oxidation into methemoglobin while sodium nitrite required an inductionary period (lag phase) prior to the reaction. Kinetic studies of the biomolecular rate law for each of the preceding reaction's reactionary periods (log phases) allowed rate constant calculations to be made. The values are 1.14 x 10(4) M-1 min-1, 7.45 x 10(4) M-1 min-1, and 3.50 x 10(1) M-1 min-1 for sodium nitrite, amyl nitrite and nitroglycerin, respectively. A comparison of the amyl nitrite and nitroglycerin rate constants reveals that amyl nitrite is approximately 2000-fold more toxic to oxyhemoglobin than nitroglycerin. These oxidant's effect on in vitro hemoglobin solutions are comparable since both reactions approximate to rectangular hyperbolae. Sodium nitrite reacts about 300-fold faster with oxyhemoglobin than does nitroglycerin. However, the sodium nitrite reaction proceeds in a sigmoidal fashion which makes a strict comparison between these compounds relative toxicities less clear cut.

Kinetics of amyl nitrite-induced hemoglobin oxidation in cord and adult blood.

The effect of amyl nitrite on the erythrocytes of adult and cord hemoglobin was examined in vitro. This study revealed that amyl nitrite caused oxyhemoglobin to become oxidized to methemoglobin wherein a rectangular hyperbolic curve was generated as the reaction progressed. This curve consisted of a reactionary log phase, and a terminal asymptotic phase only, with no inductionary lag phase. A comparative study of human cord blood oxidation times and adult blood was undertaken. It was revealed that cord blood erythrocytes were oxidized by amyl nitrite at a 5-6-fold greater rate than adult blood erythrocytes. Based on an independent Student's t-test, the time taken for cord blood erythrocytes to undergo oxidation was significantly shorter (P less than 0.05) than adult controls. This greatly enhanced reactivity of cord blood erythrocytes parallels earlier findings when sodium nitrite was used instead of amyl nitrite. However, this difference defies a simple explanation and must be attributed to many factors which may include pH, structural differences, and solubility phenomenon.

Relationship between vitamin A and iron in the liver.

Anemia associated with vitamin A deficiency and increased liver iron has implicated vitamin A in the regulation of iron release from the liver. To study this relationship further, groups of weanling rats were fed diets as follows: low iron/low vitamin A, low iron/high vitamin A, normal iron/normal vitamin A, high iron/low vitamin A and high iron/high vitamin A. After 6 weeks the animals were killed, and blood and liver samples were taken for analyses of hemoglobin, hematocrit, red blood cell count, serum and liver vitamin A, serum and liver iron and total iron-binding capacity. Low dietary iron, but not low vitamin A intake, affected hemoglobin, hematocrit and red blood cell counts but not serum vitamin A levels. Mean serum vitamin A levels were not significantly lower in groups fed high dietary iron. High dietary iron was also associated with lower mean liver vitamin A levels; these differences were statistically significant only for the low vitamin A diet group. A high vitamin A intake was associated with a significantly lower mean hepatic iron level for the high dietary iron intake group. These data support the hypothesis that vitamin A is involved in the regulation of iron release from the liver.

A study of the superficial palmar arteries using the Doppler Ultrasonic Flowmeter.

The pattern of the superficial arteries of the hand has been studied utilising the Doppler Flowmeter technique. The superficial arteries of the hand formed several diversified patterns that permitted classification into well defined categories. The arcus palmaris superficialis was complete in 84% of the hands and incomplete in 16%. The arteria digitalis palmaris communis primus took origin from the arch in 94% and from the arterial radialis indicis in 6% of the hands. The arteria princeps pollicis and radialis indicis were quite variable in their origin and frequently differed from the normal textbook description. In 52% of the subjects, the arterial patterns in the right and left hand were different with respect to one or more arteries, while they were identical in 48% of the subjects. It would be unwise to base anything more than tentative conclusions on the data so far accumulated, because of the small population used in this project and the absence of similar studies in the literature.

Lymphocyte fluorescent profiles (LFP): a possible screening technique in neoplasia.

A technique involving fluorescent protein staining and microfluorometry has been developed for measuring the lymphocyte fluorescent profile (LFP) of peripheral blood lymphocytes. In contrast to normal humans who display a regular bell-shaped curve, the profile from patients with cancer is irregular, showing a bimodal distribution of fluorescence, with a significant population of cells fluorescing at a higher relative intensity. It is suggested that this elevation in protein concentration is due to an immune response to the presence of a neoplasm, and thus this technique may prove to be a useful indicator of malignancy.

Stereoscopic anatomy: evaluation of a new teaching system in human gross anatomy.

Traditionally, human gross anatomy teaching has revolved around anatomical dissection. Unfortunately, during the last decade a number of medical schools have experienced a decrease in the number of hours allotted to gross anatomy instruction compounded by a shortage of anatomical donors. This, in turn, has served to increase the difficulties of providing students with truly effective anatomical instruction. To help overcome this problem, a stereoscopic slide-based auto-instructional program has been developed as a substitute for dissection. Evaluation data suggest that this program, while having minor limitations in terms of anatomical orientation, does provide a viable alternative to dissection.

Training teachers in the anatomical sciences.

A number of medical schools have initiated workshops to improve faculty teaching skills. Little effort, however, has been directed toward the pedagogical training of graduate students who are destined to become future medical science teachers. To help solve this problem, the faculty of the Department of Anatomy in the University of Nebraska College of Medicine recently developed a prototype teacher training program for graduate students in anatomy. Through formal course work and practical classroom experience, students are developing the skills requisite for effective teaching of the anatomical sciences. Student and faculty response to the training program has been enthusiastic, and the objectives and structure of the program can be applied to the production of competent and skilled teachers in other areas of the basic and clinical sciences.

Effects of hypophysectomy on DNCB-induced contact sensitivity in rats.

Cell-mediated immunity in hypophysectomized (HYX) and non-hypophysectomized (NHYX) rats was assessed by measuring lymph node weight and lymph node cellular proliferation responses to cutaneous application of the skin sensitizer dinitrochlorobenzene (DNCB). Differences were found in the lymph node weight assay, with the responses of the HYX rats being significantly lower than the responses of the NHYX rats. There were, however, no significant differences as measured by the lymph node cellular proliferation assay. An explanation for these contradictory results was sought by examining dose-responsiveness to DNCB. It was found that, over a range of doses of DNCB, HYX rats showed a linear dose-response relationship in terms of both lymph node weight and lymph node cellular proliferation. No dose-responsiveness was observed in NHYX rats. Since HYX rats required a greater degree of antigenic stimulation to achieve a response level equivalent to that of NHYX rats, it may be concluded that HYX rats are immunodeficient at lower antigen levels.