During the 3rd wk of postnatal life in the rat, dramatic maturational changes occur in the structure and function of the small intestine, enabling the animal to make the transition from milk to solid food. To investigate the role of GH in the regulation of this complex process, we studied postnatal intestinal maturation in the spontaneous dwarf rat, a strain of Sprague-Dawley rats with an autosomal recessive mutation in the GH gene resulting in complete but isolated GH deficiency. GH-deficient and GH-normal littermates were studied at d 7 and 14 (suckling) and d 23 (postweaned). The body weight of GH-deficient animals was inhibited by 60% at each age. Longitudinal growth of the small intestine was not inhibited, suggesting that longitudinal small bowel growth is independent of GH regulation. Mucosal cell mass was significantly lower in GH deficiency at all ages studied, and digestive hydrolase capacity per cm of intestine was significantly lower in GH-deficient postweaned animals. However, epithelial cell mass increased markedly in association with weaning and the maturation of lactase, sucrase, and aminooligopeptidase proceeded normally in GH deficiency. These data suggest that, although GH is not required for normal postnatal intestinal maturation, the mucosal epithelial hypoplasia found in GH-deficient animals suggests that GH or GH-dependent factors act as an intestinal mucosal growth factor whose function is to promote the homeostatic or steady-state regulation of mucosal epithelial growth.
Fig. 1. Anteroposterior radiograph of the proximal left femur shows lytic lesions (arrows), some with surrounding sclerosis, and mildly expansile cortical lesions in the subtrochanteric region medially (open arrow) Fig. 2A, B. Coronal Tl-weighted (A) and T2-weighted fat saturated (B) spin-echo magnetic resonance images, obtained 1 day after the radiographs, show extensive lesions in the marrow space of the subtrochanteric region and the femoral neck. The expansile lesions in the medial cortex are well seen (arrow), as are also linear and serpiginous lesions in the femoral neck, suggesting a vascular component Fig. 3. Anterior view 99myc bone scan of pelvis and proximal femora, obtained the same day as the radiographs, demonstrates no evidence of increased uptake at the lesions in the proximal left femur. There is slight asymmetry between left and right, which is attributed to patient positioning Clinical informationA previously healthy 8-year-old girl was referred for evaluation of a lesion of the left femur. She had never complained of any symptoms, but for approximately the past 9 months her parents had noticed occasional left-sided limping of variable intensity. Soon after the limp presented, the patient had been brought to the hospital for examination. The patient could not localize any site of pain causing her limp, and radiographs of the foot and ankle were normal. Due to persistent symptoms, another radiographic examination of the left hip was carried out several months later and demonstrated a lytic lesion in the proximal femur (Fig: 1). The patient was referred to our medical center for further evaluation. On examination here, an antalgic gait was noted, as well as a mild decrease in circumference of both thigh and calf of the left leg. A 1-cm leg length discrepancy was noted, the left leg being shorter. All joints of the lower extremities had full and symmetric range of motion, and there was no evidence of pain or tenderness. A magnetic resonance (MR) examination of the proximal femora (Fig. 2) had recently been performed on a 1.5-T system, and a b o n e scan (Fig.
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