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The focus of this thesis was leptin and its role in the development of obesity and non-insulin-dependent diabetes mellitus (NIDDM). Studies in Psammomys obesus, a polygenic animal model of obesity and NIDDM, showed that ob gene expression and plasma leptin concentration correlated significantly with body weight, percentage body fat and plasma insulin concentration. In addition, plasma leptin concentrations were significantly elevated in insulin resistant Psammomys obesus independent of body weight. Dietary energy restriction from weaning in Psammomys obesus prevented excessive body weight gain, hyperleptinemia and hyperglycemia compared with ad libitum fed animals. Interestingly, 19% of the energy-restricted animals still developed hyperinsulinemia and tended to have increased plasma leplin compared with normoinsulinemic energy-restricted Psammomys obesus. Fasting for 24 hours significantly reduced plasma leptin concentration in lean, insulin-sensitive but not obese, insulin-resistant P. obesus, suggesting a dysregulation in the response of leptin to acute caloric deprivation in these animals. The effects of leptin administration to P. obesus were also investigated. Single daily intraperitoneal injection of 5 mg leptin/kg body weight for 14 days had no significant effect in lean or obese P. obesus. This dose had previously been shown to rapidly and significantly reduce food intake and body weight in ob/ob and wild-type mice, suggesting relative leptin resistance in P. obesus. Acute (8 hour) effects of administration of 5 mg leptin/kg body weight were also investigated. No significant effects on food intake or plasma insulin were detected, however blood glucose concentrations were significantly elevated in obese, glucose intolerant P. obexus, suggesting an exacerbation of insulin resistance in susceptible animals. Treatment of lean, healthy P. obesus with 45 mg leptin/kg body weight/day for 7 days resulted in significant decreases in food intake and percentage body fat, showing that the leptin resistance observed in this species could be overcome by the administration of very large doses of leptin. In another study, leplin was shown to significantly inhibit maximal insulin binding to isolated adipocytes, suggesting that leptin may respresent an important link between obesity and NIDDM. Links between aspects of obesity and NIDDM and polymorphisms in the ob and p3-adrencrgic receptor genes were also investigated in two human populations.

Thesis (M.S.)--Duquesne University, 2007. / Title from document title page. Abstract included in electronic submission form. Includes bibliographical references (p. 54-60) and index.

This study was conducted to determine the effects of shipping stress on the immune system in domestic lambs (Ovis aries) and to determine the potential of the thymic peptide, thymulin, to reduce those effects of stress on the immune system. Treatments consisted of no shipping (as unstressed controls), shipping (as stressed controls) or shipping plus two doses of thymulin. The shipping procedure was conducted for two consecutive days. The responses were measured in three ways. First, the ability of peripheral blood mononuclear cells (PBMN) to respond to four different doses of the mitogen, Interleukin-2 (IL-2), was measured. Second, antibody response to a standard antigen dose over a three week period following the stress was examined. Third, the plasma cortisol concentrations in stressed versus unstressed and in thymulin treated lambs were compared. There were no differences between any of the four treatment groups (p>0.44) with respect to the animals' lymphocyte proliferative ability. Although there were no detectable differences, caution should be used in interpreting these results, because of technical difficulties encountered with a key reagent in the assay. Antibody titers were measured at weekly intervals for each of three consecutive weeks following the stressing procedure. These results also showed no treatment effect between any of the four groups (p>0.39). A comparison of cortisol levels in the four groups revealed that shipping stress increased plasma cortisol concentrations, and thymulin treatment at either dose and on both days of shipment inhibited (p<0.0001 and p<0.047, for day one and two, respectively) that stress-induced increase in cortisol. Interestingly, these results indicate that treatment with thymulin was effective in negating the stress-associated increase in plasma cortisol levels in the lambs. These in vivo data support a possible immunomodulatory function of thymulin. / Graduation date: 1997

Free weights are generally preferred over machines by practitioners of strength training because they involve incorporation of greater muscle mass because of the greater stabilization that is required. Using free weights may therefore allow one to gain more muscle mass and strength with chronic training; however, this has not been thoroughly addressed. The purpose of this study was to compare the effect of training with free weights or machines on muscle mass, testosterone and cortisol concentrations, and strength. Fifteen males and twenty-one females aged 22 ± 3 y with previous weight training experience trained using only free weights or only machines for eight weeks. Hormone concentrations were assessed via saliva samples pre and post workout at the beginning, mid-way, and end of the study. Muscle thickness, lean tissue mass, and strength were measured at the beginning and the end of the study. Elbow flexor thickness increased significantly by 3.9% and a 5.1% in the free weight group and machine group, respectively (p<0.01), with no difference between groups. Knee extensor thickness increased significantly by 4.6% and a 4.9% in the free weight group and machine group, respectively (p<0.01), with no difference between groups. No significant changes occurred in the lean tissue mass during the eight week training period. The group x time interaction for machine bench press strength was close to significance (p=0.054) with the machine training group experiencing a greater increase in strength compared to the free weight training group (13.9% vs. 8.6%). Free weight bench press, free weight squat, and Smith machine squat strength increased significantly in both groups (11-19%; p<0.01) with no difference between groups. The males in the free-weight group had a 21.7% increase in testosterone from before to after acute training sessions (p<0.01); however, the acute increase in testosterone to cortisol ratio in males training with free weights did not differ from males training on machines. Results from this study indicate that training with free weights or machines result in similar increases in muscle mass and strength, and testosterone to cortisol ratio. Males training with free weights may benefit from a greater acute increase in testosterone levels during individual training sessions.

Free weights are generally preferred over machines by practitioners of strength training because they involve incorporation of greater muscle mass because of the greater stabilization that is required. Using free weights may therefore allow one to gain more muscle mass and strength with chronic training; however, this has not been thoroughly addressed. The purpose of this study was to compare the effect of training with free weights or machines on muscle mass, testosterone and cortisol concentrations, and strength. Fifteen males and twenty-one females aged 22 ± 3 y with previous weight training experience trained using only free weights or only machines for eight weeks. Hormone concentrations were assessed via saliva samples pre and post workout at the beginning, mid-way, and end of the study. Muscle thickness, lean tissue mass, and strength were measured at the beginning and the end of the study. Elbow flexor thickness increased significantly by 3.9% and a 5.1% in the free weight group and machine group, respectively (p<0.01), with no difference between groups. Knee extensor thickness increased significantly by 4.6% and a 4.9% in the free weight group and machine group, respectively (p<0.01), with no difference between groups. No significant changes occurred in the lean tissue mass during the eight week training period. The group x time interaction for machine bench press strength was close to significance (p=0.054) with the machine training group experiencing a greater increase in strength compared to the free weight training group (13.9% vs. 8.6%). Free weight bench press, free weight squat, and Smith machine squat strength increased significantly in both groups (11-19%; p<0.01) with no difference between groups. The males in the free-weight group had a 21.7% increase in testosterone from before to after acute training sessions (p<0.01); however, the acute increase in testosterone to cortisol ratio in males training with free weights did not differ from males training on machines. Results from this study indicate that training with free weights or machines result in similar increases in muscle mass and strength, and testosterone to cortisol ratio. Males training with free weights may benefit from a greater acute increase in testosterone levels during individual training sessions.

Thèse doctorat : Pharmacie. Chimie thérapeutique : Université de Nantes : 2003. / Bibliogr. f. 188-195.

Thèse doctorat : Aspects Moléculaires et Cellulaire de la Biologie : Strasbourg 1 : 2006. / Thèse soutenue sur un ensemble de travaux. Titre provenant de l'écran-titre. Bibliogr. 19 p.

Reproduction de : Thèse de doctorat : Ecotoxicologie : Metz : 1977. / Titre provenant de l'écran-titre. Notes bibliographiques. Index.