Aged men display blunted biorhythmic variation of muscle performance and physiological responses.

Aging is known to disrupt the "biological clock" that governs physiological variables at rest. This study sought to determine whether aged men demonstrated biorhythmic variation in muscle performance during resistance exercise and physiological responses to that stimulus. Ten aged (75.6 +/- 1.6 yr; mean +/- SE) men completed an isokinetic testing protocol of knee extensors and flexors at 0800, 1200, 1600, and 2000 h. Although time of day variation in peak torque was detectable, significant (P < or = 0.05) oscillation was established only in the knee flexors at 3.14 rad/s. Heart rate, blood pressure, and rectal temperature displayed no significant variation, but trends (P < 0.10) in oscillation of postexercise blood pressure and rectal temperature were noted. Temporal patterns in biorhythmic variation of muscle performance, as well as thermal and cardiovascular measures, emulated those observed in a previous study involving young men where the magnitude of variation was sufficient to achieve statistical significance. Similar to our earlier findings in young men, however, pre- and postexercise testosterone and cortisol concentrations demonstrated significant variation among aged men. These data confirm the blunting of biorhythmic variation in muscle performance and physiological variables, except for circulating hormones, in aged men.     

Applications of NMR to structure-based drug design in structural genomics

Structural genomics is poised to have a tremendous impact on traditional structure-based drug design programs. As a result, there is a growing need to obtain rapid structural information in a reliable form that is amenable to rational drug design. In this manner, NMR has been expanding and evolving its role in aiding the design process. A variety of NMR methodologies that cover a range of inherent resolution are described in the context of structure-based drug design in the era of structural genomics.     

Inhibition of arginine gingipains (RgpB and HRgpA) with benzamidine inhibitors: zinc increases inhibitory potency

We assayed several benzamidine derivatives for inhibition potency with HRgpA and RgpB gingipains, enzymes which are involved in the pathogenesis of gingivitis and periodontal disease. The benzamidine derivatives proved to be effective inhibitors of HRgpA and RgpB, with the best inhibitor being a bis-benzamidine with a urea linker (Ki=30 microM). The inhibition potency was increased 2-3 fold in the presence of low concentrations of zinc with the benzamidines containing a urea moiety linking the two aromatic rings. We propose an inhibition model involving a tetrahedral zinc atom coordinated with the active site Cys and His of gingipain and the urea linker in the benzamidine inhibitor. In summary, we have discovered a new series of effective inhibitors for the gingipains and found a novel way to increase inhibitor potency with the HRgpA and RgpB gingipains using zinc.     

Effect of Rainbow Trout Growth Hormone Complementary DNA on Body Shape,Carcass Yield,and Carcass Composition of F1 and F2 Transgenic Common Carp (Cyprinus carpio

The effect of rainbow trout growth hormone complementary DNA on body shape, dress-out yield, and body composition were assessed in the F1 and F2 generations of transgenic common carp (Cyprinus carpio). All measurements were compared with those for nontransgenic full-sibling common carp in their respective families, and the fish were communally evaluated in earthen ponds. The body weight and length were highly correlated (P <0.01) in both genotypes in all the families. Head morphometrics were negatively correlated (P <0.05) to weight and length of the fish. Various head, body, and caudal traits grew disproportionately faster in transgenic fish in both generations. The altered body shape of transgenic fish resulted in improved dressing percentage in the F2 generation. The carcass composition of transgenic muscle had a lower percentage of (P <0.01) moisture and lipids and higher (P <0.01) percentage of protein in both generations. Six of the 18 amino acids analyzed in F1 transgenic common carp muscle were higher F1 (P <0.05) than the control genotype; however, amino acid ratios were minimally changed. Also, the fatty acid profiles of both genotypes were minimally altered. Higher histidine and lysine ratios in the diet are recommended for maximum growth and health of transgenic common carp in intensive culture systems on the basis of essential amino acid ratios.     

Aza-peptide epoxides: potent and selective inhibitors of Schistosoma mansoni and pig kidney legumains (asparaginyl endopeptidases)

Aza-peptide epoxides are a new class of irreversible cysteine protease inhibitors. Derivatives containing a P1 aza-asparagine residue are specific for Schistosoma mansoni and pig kidney legumains, which are clan CD cysteine proteases. The inhibitors have second-order rate constants of up to 10(4) M(-1) s(-1) with pig kidney legumain and IC50 values as low as 45 nM with S. mansoni legumain. The most potent epoxides contain an ester moiety with S,S stereochemistry attached to the epoxide. Interestingly, amide and amino acid derivatives of the epoxysuccinate moiety were not inhibitors of legumain, while disubstituted amide derivatives are quite potent. The inhibitors have little or no inhibitory activity with other proteases such as caspases, chymotrypsin, papain, cathepsin B, granzyme B, and various aspartyl proteases.     

Are hummingbirds facultatively ammonotelic? Nitrogen excretion and requirements as a function of body size

Most birds are uricotelic. An exception to this rule may be nectar-feeding birds, which excrete significant amounts of ammonia under certain conditions. Although ammonia is toxic, because it is highly water soluble its excretion may be facilitated in animals that ingest and excrete large amounts of water. Bird-pollinated plants secrete carbohydrate- and water-rich floral nectars that contain exceedingly little protein. Thus, nectar-feeding birds are faced with the dual challenge of meeting nitrogen requirements while disposing of large amounts of water. The peculiar diet of nectar-feeding birds suggests two hypotheses: (1) these birds must have low protein requirements, and (2) when they ingest large quantities of water their primary nitrogen excretion product may be ammonia. To test these hypotheses, we measured maintenance nitrogen requirements (MNR) and total endogenous nitrogen losses (TENL) in three hummingbird species (Archilochus alexandri, Eugenes fulgens, and Lampornis clemenciae) fed on diets with varying sugar, protein, and water content. We also quantified the form in which the by-products of nitrogen metabolism were excreted. The MNR and TENL of the hummingbirds examined were exceptionally low. However, no birds excreted more than 50% of nitrogen as ammonia or more nitrogen as ammonia than urates. Furthermore, ammonia excretion was not influenced by either water or protein intake. The smallest species (A. alexandri) excreted a significantly greater proportion (>25%) of their nitrogenous wastes as ammonia than the larger hummingbirds ( approximately 4%). Our results support the hypothesis that nectar-feeding birds have low protein requirements but cast doubt on the notion that they are facultatively ammonotelic. Our data also hint at a possible size-dependent dichotomy in hummingbirds, with higher ammonia excretion in smaller species. Differences in proportionate water loads and/or postrenal modification of urine may explain this dichotomy.     

Influence of normal daytime fat deposition on laboratory measurements of torpor use in territorial versus nonterritorial hummingbirds

Fat deposition and torpor use in hummingbirds exhibiting distinct foraging styles should vary. We predicted that dominant territorial hummingbirds will use torpor less than subordinate nonterritorial species because unrestricted access to energy by territory owners allows for fat storage. Entry into torpor was monitored using open-flow respirometry on hummingbirds allowed to accumulate fat normally during the day. Fat accumulation was measured by solvent fat extraction. Territorial blue-throated hummingbirds (Lampornis clemenciae) had the highest fat accumulation and used torpor only 17% of the time. Fat storage by L. clemenciae averaged 26% of lean dry mass (LDM) in 1995 and 18% in 1996, similar to that measured for other nonmigratory birds. Fat storage by magnificent hummingbirds (Eugenes fulgens; trapliner) and black-chinned hummingbirds (Archilochus alexandri; nectar robber) averaged 19% and 16% of LDM, respectively, and they used torpor frequently (64% and 92% of the time, respectively). All species initiated torpor if total body fat dropped below 10% of LDM, indicating the existence of a torpor threshold. The ability of L. clemenciae to store enough fat to support nighttime metabolism is likely an important benefit of territoriality. Likewise, frequent torpor use by subordinates suggests that natural restrictions to energy intake can impact their energy budget, necessitating energy conservation by use of torpor.     

Role of ALDP (ABCD1) and mitochondria in X-linked adrenoleukodystrophy

Peroxisomal disorders have been associated with malfunction of peroxisomal metabolic pathways, but the pathogenesis of these disorders is largely unknown. X-linked adrenoleukodystrophy (X-ALD) is associated with elevated levels of very-long-chain fatty acids (VLCFA; C(>22:0)) that have been attributed to reduced peroxisomal VLCFA beta-oxidation activity. Previously, our laboratory and others have reported elevated VLCFA levels and reduced peroxisomal VLCFA beta-oxidation in human and mouse X-ALD fibroblasts. In this study, we found normal levels of peroxisomal VLCFA beta-oxidation in tissues from ALD mice with elevated VLCFA levels. Treatment of ALD mice with pharmacological agents resulted in decreased VLCFA levels without a change in VLCFA beta-oxidation activity. These data indicate that ALDP does not determine the rate of VLCFA beta-oxidation and that VLCFA levels are not determined by the rate of VLCFA beta-oxidation. The rate of peroxisomal VLCFA beta-oxidation in human and mouse fibroblasts in vitro is affected by the rate of mitochondrial long-chain fatty acid beta-oxidation. We hypothesize that ALDP facilitates the interaction between peroxisomes and mitochondria, resulting, when ALDP is deficient in X-ALD, in increased VLCFA accumulation despite normal peroxisomal VLCFA beta-oxidation in ALD mouse tissues. In support of this hypothesis, mitochondrial structural abnormalities were observed in adrenal cortical cells of ALD mice.