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Biomedical subjects

L McFadden

Publications and source records attributed to L McFadden.

6 recordsLinked to original sources
PubMed1997

Depression of human electromyographic activity by fatigue of a synergistic muscle.

In human volunteers, lateral gastrocnemius muscles were stimulated electrically under ischemic conditions so as to produce fatigue. Recordings of electromyographic (EMG) activity were then made from those muscles and simultaneously from untreated medial gastrocnemius muscles during maximal voluntary efforts. In the lateral gastrocnemius the mean amount of EMG activity declined by 52% and was associated with a 35% reduction in the mean amplitude of the M wave (muscle compound action potential) and an insignificant change in M-wave area. In the medial gastrocnemius the EMG was also diminished, by 29%, but there were no significant changes in M-wave amplitude or area. The findings in the medial gastrocnemius are consistent with the existence of an inhibitory reflex effect which originates in the fatigued lateral gastrocnemius muscle and serves to depress excitation in motoneurons supplying that muscle and also in those innervating synergists. The inhibitory effect appears to be long-lasting, in that a significant reduction of the EMG could still be demonstrated 10 min after release of the arterial cuff.

Adolescent↗
PubMed1997

Spatial resolution of transdermal water mobility using NMR microscopy.

High resolution images were obtained using high-field nuclear magnetic resonance microscopy of in vitro preparations of hydrated hairless rat skin. The major anatomical features observed were comparable to those seen by electron microscopy and include the stratum corneum, the viable epidermis, sebaceous glands, the cell layers surrounding hair follicles (the outer and inner root sheaths), and regions of subcutaneous fatty deposits. Calculated diffusion maps demonstrated that signal intensity is sufficient to obtain quantitative water mobility data from the viable epidermis and the hair follicle/sebaceous gland regions. Images from skin immersed in D2O clearly distinguish signal contributions that arise from fat from those which arise from water, and indicate that the calculated diffusion maps include only proton mobility from water in skin. These results may lead to further applications for using quantitative nuclear magnetic resonance microscopy for examining transdermal transport processes of in vitro skin preparations.

Animals↗
PubMedDate not supplied

Dominant lethal gene test of 5-thio-D-glucose in male mice.

Genetic effects of 5-thio-D-glucose (5-thio) were tested in male mice by the dominant lethal gene test. Males were treated with phosphate buffered saline (PBS) or 5-thio dissolved in PBS by oral intubation daily at 40 or 60 mg/kg for 7 or 35 successive days. Average implantations per pregnant female and the intrauterine postimplantation losses in females mated with 5-thio trated males did not show any significant differences when compared statistically with parallel controls. Furthermore, the compound had no effect on the appearance and mating behavior of the male mice. This is the first report on the genetic effects of 5-thio to show that the compound in the treatment regimens studied were not mutagenic in terms of the induction of dominant lethal mutation in male mice.

Animals↗