Caffeine, cycling performance, and exogenous CHO oxidation: a dose-response study.

PURPOSE: This study investigated the effects of a low and moderate caffeine dose on exogenous CHO oxidation and endurance-exercise performance. METHODS: Nine trained and familiarized male cyclists (mean +/- SD: 29.4 +/- 4.5 yr, 81.3 +/- 10.8 kg body weight [BW], 183.8 +/- 8.2 cm, V O2peak = 61.7 +/- 4.8 mL.kg.min) undertook three trials, with training and high CHO diet being controlled. One hour before exercise, subjects ingested capsules containing placebo and 1.5 or 3 mg.kg BW of caffeine using a double-blind administration protocol. Trials consisted of 120 min steady-state cycling at approximately 70% V O2peak, immediately followed by a 7-kJ.kg BW time trial (TT). During exercise, subjects were provided with fluids containing C-glucose every 20 min to determine exogenous CHO oxidation. RESULTS: No significant TT performance improvements were observed during caffeine-containing trials (mean +/- SD: placebo = 30 min 25 s +/- 3 min 10 s; 1.5 mg.kg BW = 30 min 42 s +/- 3 min 41 s; and 3 mg.kg BW = 29 min 51 s +/- 3 min 38 s). Furthermore, caffeine failed to significantly alter maximal exogenous CHO oxidation (maximal oxidation rates: placebo = 0.95 +/- 0.2 g.min; 1.5 mg.kg BW = 0.92 +/- 0.2 g.min; and 3 mg.kg BW = 0.96 +/- 0.2 g.min). CONCLUSION: Low and moderate doses of caffeine have failed to improve endurance performance in fed, trained subjects.

L-Serine regulates the activities of microglial cells that express very low level of 3-phosphoglycerate dehydrogenase, an enzyme for L-Serine biosynthesis.

Microglia are well known to become activated during various kinds of neuropathological events. The factors that are responsible for the activation, however, are not fully determined. In the present study, L-Ser was shown to enhance production of nitric oxide (NO), interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF alpha) by lipopolysaccharide (LPS)-stimulated cultured rat microglial cells. L-Ser, however, did not enhance the expression of mRNAs encoding inducible NO synthase, IL-6 and TNF alpha. On the other hand, astrocytes did not depend on L-Ser for release of IL-6 and TNF alpha. The expression of an enzyme 3-phosphoglycerate dehydrogenase (3PGDH), which is essential for L-Ser biosynthesis from a glycolytic intermediate 3-phosphoglycerate, was investigated. As revealed by Western blotting and immunocytochemical staining, 3PGDH-protein expression in vitro was the highest in astrocytes, intermediate in neurons and the lowest in microglial cells. Semiquantitative RT-PCR showed that microglial cells expressed 3PGDH-mRNA at a lower level than astrocytes. In frozen sections from rat forebrain, only astrocytes were immunoreactive for 3PGDH. The present study suggested that L-Ser is able to modulate microglial function mainly at the translation level because microglial cells cannot synthesize sufficient amount of L-Ser due to the scarce expression of 3PGDH.

A novel NADP(+)-dependent serine dehydrogenase from Agrobacterium tumefaciens.

NADP(+)-dependent serine dehydrogenase [EC 1.1.1.-], which catalyzes the oxidation of the hydroxyl group of serine to form 2-aminomalonate semialdehyde, was purified to homogeneity from a crude extract of Agrobacterium tumefaciens ICR 1600. The enzyme had a molecular mass of about 100 kDa and consisted of four identical subunits. In addition to L-serine, D-serine, L-glycerate, D-glycerate, and 2-methyl-DL-serine were substrates. However, O-methyl-DL-serine and L-threonine were inert. The enzyme showed maximal activity at about pH 9 for the oxidation of L-serine. The enzyme required NADP+ as a coenzyme, NAD+ was inert. The enzyme was not inhibited by EDTA, o-phenanthroline, or alpha,alpha'-dipyridyl, but was inhibited by HgCl2, p-chloromercuribenzoate, L-cysteine, D-cysteine, malonate, 2-methylmalonate, and tartronate. The Michaelis constants for L-serine, D-serine, and NADP+ were 42, 44, and 0.029 mM, respectively.

[Effect of lignin preparations and cultivation conditions on the ligninolytic complex of the fungus Pleurotus floridae, the wood white-rot pathogen]. / Vliianie preparatov lignina i uslovii kyl'tivirovaniia na ligninoliticheskii kompleks griba Pleurotus floridae-- vozbuditelia beloi gnili drevesiny.

Effect of various cultivation conditions and lignin preparations on the enzymes of ligninolytic enzyme complex of white-rot fungus Pleurotus floridae has been studied. The maximal Mn-peroxidase activity was revealed in the medium with low nitrogen content (1.2 mM); maximal values of cellobiose quinone oxidoreductase activity were observed in the media with high nitrogen content (7.2 mM); maximal values of laccase activity in the media with low content of glucose (2 g/l) during Pleurotus floridae cultivation in Kirk's stationary cultures have been shown. Employment of submerged cultivation under conditions of mycelium immobilization on polyurethane carriers allowed us to increase laccase activity twice as compared with cultivation in small stationary cultures, while had the crucial effect on the Mn-peroxidase activity. The selective effect of the studied lignin preparations on the components of ligninolytic complex and their isoenzymes has been stated. The dependence of laccase and Mn-peroxidase activities on high and low-molecular weight fractions balance in lignin preparations has been established.

Effects of ethanol treatment on Leydig cellular NADPH-generating enzymes and lipid profiles.

Effects of ethanol treatment on Leydig cell NADPH-generating enzymes and lipid profiles were studied. Ethanol treatment (3.0 g/kg b.wt.) twice daily as a 25% (v/v) aqueous solution given to adult Wistar rats reduced the body weight, testis weight and relative weights of the seminal vesicles and ventral prostate. Serum LH and testosterone were also decreased. Similarly, the NADPH-generating enzymes such as G-6-PDH, 6-PGDH, NADP-ICDH were reduced, but malic enzyme was unaltered. Leydig cell total lipid was decreased: neutral lipids such as esterified cholesterol and triacyl glycerol were decreased but free cholesterol and diacyl glycerol were increased. The reduction in total phospholipid was contributed to by fractions such as phosphatidyl inositol, phosphatidyl serine, phosphatidyl choline and phosphatidyl ethanolamine. Withdrawal of ethanol treatment for 30 days restored these to the normal level. The present findings suggest that the ethanol treatment impairs Leydig cellular NADPH generation which may be one of the biochemical mechanisms mediating the direct and indirect effects of ethanol resulting in hypoandrogenization.