Laura K. Stewart

Cographs are the graphs formed from a single vertex under the closure of the operations of union and complement. Another characterization of cographs is that they are the undirected graphs with no induced paths on four vertices. Cographs arise naturally in such application areas as examination scheduling and automatic clustering of index terms. Furthermore, it is known that cographs have a unique tree representation called a cotree. Using the cotree it is possible to design very fast polynomial time algorithms for problems which are intractable for graphs in general. Such problems include chromatic number, clique determination, clustering, minimum weight domination, isomorphism, minimum fill-in and Hamiltonicity. In this paper we present a linear time algorithm for recognizing cographs and constructing their cotree representation.

PURPOSE: The purpose of this study was to examine the influence of a 12-wk exercise training program on inflammatory cytokine and C-reactive protein (CRP) concentrations. A secondary purpose was to determine whether training-induced changes in cytokines and CRP were influenced by age. METHODS: Twenty-nine younger (18-35 yr) and 31 older (65-85 yr) subjects were assigned to young physically active (YPA, N = 15; 25 +/- 5 yr), young physically inactive (YPI, N= 14; 25 +/- 4.7 yr), old physically active (OPA, N = 14; 71 +/- 4 yr), or old physically inactive (OPI, N = 17; 71 +/- 4 yr) groups. The inactive groups completed 12 wk (3 d.wk) of aerobic and resistance exercises, and the physically active control groups continued their normal exercise programs. Blood samples were collected before and after the 12-wk period, and the concentrations of serum CRP, plasma interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-alpha), and interleukin-1 beta (IL-1beta) were determined using separate ELISA. RESULTS: Control (YPA and OPA) estimated VO2max was unchanged. Exercise training increased estimated VO2max an average of 10.4% and increased strength by an average of 38.1% in both PI groups. Serum CRP decreased with training (YPI and OPI) groups and was not different from the YPA and OPA groups after training. Plasma IL-6 and IL-1beta did not change, whereas TNF-alpha was higher than YPI and YPA at baseline and after the intervention period. CONCLUSION: These results support the use of combined aerobic/resistance training as a modality to reduce the risk of cardiovascular disease development as defined by a decrease in serum CRP concentration in healthy humans.

Dietary methionine restriction (MR) is a mimetic of chronic dietary restriction (DR) in the sense that MR increases rodent longevity, but without food restriction. We report here that MR also persistently increases total energy expenditure (EE) and limits fat deposition despite increasing weight-specific food consumption. In Fischer 344 (F344) rats consuming control or MR diets for 3, 9, and 20 mo, mean EE was 1.5-fold higher in MR vs. control rats, primarily due to higher EE during the night at all ages. The day-to-night transition produced a twofold higher heat increment of feeding (3.0 degrees C vs. 1.5 degrees C) in MR vs. controls and an exaggerated increase in respiratory quotient (RQ) to values greater than 1, indicative of the interconversion of glucose to lipid by de novo lipogenesis. The simultaneous inhibition of glucose utilization and shift to fat oxidation during the day was also more complete in MR (RQ approximately 0.75) vs. controls (RQ approximately 0.85). Dietary MR produced a rapid and persistent increase in uncoupling protein 1 expression in brown (BAT) and white adipose tissue (WAT) in conjunction with decreased leptin and increased adiponectin levels in serum, suggesting that remodeling of the metabolic and endocrine function of adipose tissue may have an important role in the overall increase in EE. We conclude that the hyperphagic response to dietary MR is matched to a coordinated increase in uncoupled respiration, suggesting the engagement of a nutrient-sensing mechanism, which compensates for limited methionine through integrated effects on energy homeostasis.