Serum leptin is increased in growth hormone-deficient adults: relationship to body composition and effects of placebo-controlled growth hormone therapy for 1 year

The gene product from the ob gene, leptin, has recently been characterized in humans. The circulating level of leptin is related to body mass index (BMI) and more closely to estimates of total body fat, whereas visceral fat has been reported to be of minor importance. However, it is unknown if leptin is directly regulated by hormones that influence substrate metabolism and body composition. We studied leptin in adult growth hormone (GH)-deficient (GHD) patients substituted with GH treatment for 12 months in a parallel double-blind, placebo-controlled study. Twenty-seven GHD adults aged 44.9 +/- 1.9 years underwent anthropometric measurements for determination of regional and total body fat (BMI, waist to hip ratio [WHR], computed tomographic [CT] scan, dual-energy x-ray absorptiometry [DEXA] scan, and bioimpedance analysis [BIA]) before and after 12 months of placebo-controlled GH substitution (2 IU/m2) in a parallel design. The same measurements were performed in 42 healthy adults aged 39.1 +/- 1.7 years. The logarithm of serum leptin levels correlated positively with abdominal subcutaneous fat and total body fat (BIA and DEXA) in untreated GHD patients and healthy subjects. Fasting insulin did not correlate with leptin levels in either of the groups. After 12 months of GH administration, the body composition of GHD patients was significantly changed with respect to a marked decrease in body fat. The relations of leptin to the estimates of body fat were maintained, and leptin was furthermore related to BMI and fasting insulin. In multiple linear regression analyses, additional estimates of visceral adiposity (intraabdominal fat and maximal anterior-posterior diameter determined by CT scan) were significant determinants of leptin in the healthy subjects. The increase in fasting insulin levels during GH substitution correlated negatively with the reduction in leptin levels (r = -.823, P = .003). At baseline, leptin levels were increased in the patients compared with controls in both sexes (women, 21.8 +/- 3.3 v 11.3 +/- 1.4 ng/mL, P = .002; men, 8.1 +/- 1.2 v 4.7 +/- 0.7 ng/mL, P = .008). Leptin levels were similar in GHD patients treated for 12 months compared with healthy controls for both women and men (women, 15.9 +/- 2.3 and 11.3 +/- 1.4 ng/mL, P = .163; men, 7.1 +/- 2.8 and 4.7 +/- 0.7 ng/mL, P = .759). In healthy adults and in GHD patients, leptin levels were significantly higher in women than in men (11.3 +/- 1.4 v 4.7 +/- 0.7 ng/mL, P < .001; 21.8 +/- 3.3 v 8.1 +/- 1.2 ng/mL, P < .001). Gender remained a significant determinant of leptin levels in several models of multiple linear regression analysis also including age, estradiol levels, insulin, and estimates of body fat. We conclude that leptin is increased but not differently regulated in GHD patients compared with normal subjects, and that leptin levels are closely related to estimates of body fat. This relationship is maintained during a decrease in body fat due to GH substitution.     

Wideband diffraction compensation methods and the angular spectrumof waves (ASoW) model for TV SAW filters

Wideband diffraction compensation methods are reviewed. Eight algorithms are formulated, implemented, and tested for evaluating their performance. The angular spectrum of waves (ASoW) model for diffraction analysis is derived and validated by comparing measurements and analysis results. And, the most robust compensation algorithm is applied with the ASoW analysis program to design SAW filters. Both internal reflections and end effects are considered in the analysis and compensation programs. This paper also demonstrates that the ASoW model is superior to parametric diffraction models such as the parabolic approximation model as far as formulation, implementation, calculation speed, and generality are concerned     

Effect of calcaneal lengthening on relationships among the hindfoot, midfoot, and forefoot

To better understand the bony component of pes planus and the means by which the Evans calcaneal lengthening corrects them, we studied the standing radiographs of seven adult patients who had undergone calcaneal lengthening to treat symptomatic pes planus. Weightbearing AP and lateral views done preoperatively and postoperatively were used for the study. For each set of films, the following parameters were measured: on the lateral view; overall length of the calcaneus, lateral talometatarsal angle, lateral talocalcaneal angle, and the calcaneal pitch angle; and on the dorsoplantar view, the talometatarsal and talocalcaneal angle. In addition, the relative coverage of the talus by the navicular was described by an angular measurement based on the relationship of the center of the talus to the center of the navicular. The average improvements in lateral talocalcaneal angle (a reflection of hindfoot valgus) was 6.4 degrees when the long axis of the calcaneus was used and 6.8 degrees when the inferior surface of the calcaneous was used for the measurement. The lateral talometatarsal angle improved an average 11.3 degrees (from an average of 19.7 degrees to 8.4 degrees). The dorsoplantar talometatarsal angle (a measure of forefoot adduction/abduction) improved 15.8 degrees (preoperative average 26.8 degrees, postoperative average 11 degrees). The calcaneal pitch angle improved an average 10.8 degrees (preoperative average 3.2 degrees, postoperative average 14 degrees). The relationship between the talus and navicular was defined by an angular measurement based on the center of each articular surface before and after correction using this measurement. An average improvement of 26 degrees occurred in the alignment of these two articular surfaces.(ABSTRACT TRUNCATED AT 250 WORDS)     

Prediction of stresses in concrete pavements subjected to non-linear gradients

This paper presents a technique for analyzing the residual stresses in concrete pavements subjected to non-linear (stress or strain) gradients throughout the slab thickness. The analysis is separated into two parts. In the first part, an expression is presented for calculating the self equilibrated stresses within a cross-section due to internal restraints (i.e. satisfying equilibrium conditions and continuity of the strain field within the cross-section). These stresses are independent of slab dimensions and boundary conditions. In step two, the stresses due to external restraints (i.e. self-weight and subgrade reaction) are calculated using an equivalent linear temperature gradient obtained from the first part and using existing closed form solutions by Westergaard [Westergaard, H. M., Computation of stresses in concrete roads. In Proc. of the 5th Annual Meeting, Vol. 5, Part I, Highway Research Board, 1926, pp. 90–112] or Bradbury [Bradbury, R. D., Reinforced Concrete Pavements. Wire Reinforcement Institute, Washington D.C., 1947.]. The solution to this step includes slab length and boundary conditions. Total internal stresses due to non-linear gradients are obtained using the superposition principle. The proposed method has been applied to field data from another study for varying temperature profiles within a 24 h period and compared to results from conventional analysis assuming linear gradients. Significant differences were found between the two methods for night-time and early-morning conditions. A linear gradient solution sometimes underestimates tension in the bottom of a slab prior to vehicle loading by a factor of three.     

Evaluation of a proton magnetic resonance technique for analysis of rubber in guayule

Low-resolution proton magnetic resonance (PMR) has been advocated as a rapid screening technique to determine rubber in guayule (Parthenium argentatum Gray). The technique was evaluated in two laboratories against a modification of the Soxhlet procedure using samples of guayule material collected from three varieties over a 3-year period. At each laboratory, significant relationships between PMR signal and extracted rubber content were found for all varieties. Regressions had statistically similar slopes between varieties, but at one laboratory the intercept of one variety differed from the intercept of the regressions of the other two varieties. It was concluded that the rapidity of the PMR technique was suited to coarse comparative studies of rubber content in guayule. For absolute assessment and within varieties, rapid estimates of rubber content using PMR can be made only after establishing a specific PMR: solvent rubber relationship on similarly treated material.     

影响声表面波振荡器的频率稳定性因素分析

本文阐述了影响声表面波振荡器频率稳定性的主要因素;探讨了改善声表面波振荡器频率稳定性的方法。