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T J LoRusso

Publications and source records attributed to T J LoRusso.

5 recordsLinked to original sources
PubMed1997

Effect of insulin-like growth factor I and/or growth hormone on diaphragm of malnourished adolescent rats.

Young growing animals appear to have significantly reduced "nutritional to short periods of unstressed starvation compared with adults, with resultant growth arrest and/or atrophy of diaphragm (Dia) muscle fibers. The aim of this study was to assess in an adolescent rat model of acute nutritional deprivation (ND; 72 h) the impact of insulin-like growth factor I (IGF-I), with or without added growth hormone (GH), on the cross-sectional areas (CSA) of individual Dia muscle fibers. Five groups were studied: 1) control (Ctr); 2) ND; 3) ND given IGF-I (ND/IGF-I); 4) ND given GH (ND/GH); and 5) ND given a combination of IGF-I and GH (ND/IGF-I/GH). IGF-I was given by a subcutaneously implanted osmotic minipump (200 microg/day), whereas GH was administered twice daily by a subcutaneous injection (250 microg every 12 h). Isometric contractile and fatigue properties of the Dia were determined in vitro. Forces were normalized for muscle CSA (i.e., specific force). Dia fiber type proportions were determined histochemically, and fiber CSA was quantified by using a computer-based image-processing system. Total serum IGF-I concentrations were significantly reduced in ND and ND/GH animals, compared with Ctr, and elevated in the groups receiving IGF-I. The provision of growth factors did not alter the contractile or fatigue properties of ND animals. Dia fiber type proportions were similar among the groups. In ND animals, there was a significant reduction in the CSA of types I, IIa, IIx, and IIc Dia fibers compared with Ctr. The administration of IGF-I alone or in combination with GH to ND animals significantly diminished the reduction in Dia fiber size. GH alone had no effect on Dia fiber size in ND animals. We conclude that with acute ND the peripheral resistance to the action of GH appears to be bypassed by the administration of IGF-I alone or in combination with GH.

Animals↗
PubMed1997

Anabolic influences of insulin-like growth factor I and/or growth hormone on the diaphragm of young rats.

It is controversial whether insulin-like growth factor I (IGF-I), growth hormone (GH), or their combination might enhance body growth and/or tissue anabolism in the well-fed animal with an intact somatotrophic axis. To assess this further, we studied four groups of adolescent rats: 1) control (Ctr), 2) GH, 3) IGF-I, and 4) GH/IGF-I. IGF-I was given via an osmotic minipump, whereas GH was injected subcutaneously for a period of 72 h. Diaphragm (Dia) contractile and fatigue properties were determined in vitro. Quantitative histochemical and morphometric analyses were performed on Dia fibers. Total serum IGF-I levels were significantly increased in the groups receiving growth factors. Although body weight increased to a greater extent in the animals receiving growth factors, a further synergistic effect was noted in the GH/IGF-I animals compared with either GH or IGF-I groups. Costal Dia mass was greater in the groups receiving growth factors. The Dia of GH/IGF-I animals was more fatigue resistant than the Dia in Ctr. The cross-sectional area of types IIa and IIx fibers were increased to a similar extent in all groups receiving growth factors compared with Ctr. Succinate dehydrogenase activity of type IIa fibers was significantly greater in the GH/IGF-I animals compared with the other groups. We conclude that the short-term provision of growth factors to well-nourished, normally growing adolescent rats can accelerate body growth and promote selective hypertrophy of predominantly type II Dia fibers.

Animals↗
PubMed1993

Prediction of maximal exercise capacity in obstructive and restrictive pulmonary disease.

We evaluated the predictive value of resting pulmonary function tests (PFTs) in the determination of maximal exercise capacity in patients with obstructive and restrictive ventilatory disease. We performed resting PFTs and an incremental exercise study on a bicycle ergometer in 146 patients with chronic obstructive pulmonary disease (COPD) and 68 patients with restrictive disease. The patients with obstructive disease were further subdivided into mild, moderate, and severe based on the severity of their airway obstruction (mean +/- SD:FEV1, 2.78 +/- 0.77, 2.12 +/- 0.74, and 1.06 +/- 0.47, respectively). Correlation coefficients for PFTs vs VO2max and VEmax in restricted patients was generally low (DL = 0.67 and 0.34, IC = 0.58 and 0.35, FVC = 0.57 and 0.35, TLC = 0.35 and 0.18). In patients with COPD, the maximum voluntary ventilation (MVV) was the single best predictor of VO2 in all groups with correlation coefficients of 0.75, 0.69, and 0.89 in the mild, moderate, and severe subgroups, respectively. Similarly, the MVV was the best predictor of VEmax in all groups with correlation coefficients of 0.59, 0.64, and 0.89 in the three subgroups. The correlation with FEV1 was slightly less for both VO2max (0.69, 0.65, and 0.87) and VEmax (0.52, 0.64, 0.64) in the mild, moderate, and severe subgroups, respectively. Our findings show that PFTs are unreliable in predicting VEmax and VO2max in restricted patients. In patients with obstruction, the MVV is the single best predictor of VO2max and VEmax in all three categories, but was not significantly improved by stepwise multiple regression with additional PFT variables. Higher correlations were obtained in the severe group in whom the correlation with VO2max and VEmax was 0.89. However, the 95 percent confidence interval of the estimate for VO2 and VE was relatively large (+/- 0.16 L/min and +/- 6.6 L/min, respectively). We conclude that although several PFTs correlate significantly with maximum exercise, the large variance precludes their use to accurately predict maximum performance in individual patients with COPD.

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