Journal of Applied Physiology, Vol 77, Issue 1 43-50, Copyright © 1994 by American Physiological Society
Total parenteral nutrition does not improve diaphragm development in premature baboons
L. C. Maxwell, T. J. Kuehl, K. Meredith, D. R. Gerstmann and R. A. Delemos
Department of Physiology, University of Texas Health Science Center, San Antonio 78284.
We hypothesized that total parenteral nutrition accelerates growth and
development of diaphragm muscle (DPH) in prematurely delivered baboons (140
days gestation). For 10 days after delivery by cesarean section, we
administered parenteral nutrition containing glucose, electrolytes, and
water or total parenteral nutrition containing lipids, amino acids,
glucose, vitamins, and electrolytes. After 10 days of care, dorsolateral
and ventrolateral (VL) costal DPH were sampled for histochemically
determined mean fiber area (MFA) and fiber type percentages. We determined
isolated bundle isometric tension (normalized for cross-sectional area),
time to peak tension, half-relaxation time, force-frequency relationship,
and fatigability. Neither sex nor nutritional treatment affected
contractile properties. Differences among sexes and muscle sites, but not
among nutritional treatments, were observed for histochemical
characteristics. In females, the VL DPH had a lower percentage of type IIo
fibers and a greater MFA of type IIc fibers than the dorsolateral DPH and a
lower percentage of type IIo fibers and greater MFA of type IIc and IIo
fibers than the VL DPH in males. Mean fiber cross-sectional area of VL DPH
was significantly greater in females than males. The larger fibers in
females than males suggest a stronger DPH in females. Earlier growth of
type II fibers in females could contribute to a better outcome for female
than male premature infants with hyaline membrane disease.
