Metabolic Changes in Rat Brain After Prolonged Ethanol Consumption Measured by 1H and 31P MRS Experiments

SUMMARY 1. In vivo ¹H and ³¹P magnetic resonance spectroscopy techniques were applied to reveal biochemical changes in the rat brain caused by prolonged ethanol consumption.2. Three models of ethanol intoxication were used.3. ¹H MRS showed a significant decrease in the concentration of myo-inositol in the brain of rats fed with 20% ethanol for 8 weeks. This change is consistent with perturbances in astrocytes. On the other hand, N-acetyl aspartate and choline content did not differ from controls.4. ³¹P MRS did not reveal any significant changes in the high-energy phosphates or intracellular free Mg²⁺ content in the brain of rats after 14 weeks of 20% ethanol drinking. The intracellular pH was diminished.5. By means of a ³¹P saturation transfer technique, a significant decrease was observed for the pseudo first-order rate constant k _for of the creatine kinase reaction in the brain of rats administered 30% ethanol for 3 weeks using a gastric tube.6. The ¹H MRS results may indicate that myo-inositol loss, reflecting a disorder in astrocytes, might be one of the first changes associated with alcoholism, which could be detected in the brain by means of in vivo ¹H MRS.7. The results from ³¹P MRS experiments suggest that alcoholism is associated with decreased brain energy metabolism.8. ³¹P saturation transfer, which provides insight into the turnover of high-energy phosphates, could be a more suitable technique for studying the brain energetics in chronic pathological states than conventional ³¹P MRS.     

Enzymes as molecular automata: a stochastic model of self-oscillatory glycolytic cycles in cellular metabolism

A stochastic model based on the molecular automata approach was developed to simulate the cyclic dynamics of glycolysis-gluconeogenesis in cell energy metabolism. The stochastic algorithm, based on Gillespie's method, simulates the master equation associated with any network of enzymatically controlled reactions. This model of the glycolytic-gluconeogenetic cycle was developed by assembling the stochastic kinetic reactions controlled by two enzymes: phosphofructokinase (PFKase) and fructose-1, 6-biphosphatase (FBPase). In order to obtain the hysteresis behaviour predicted by classical Sel'kov analysis, a minimum complexity is required in the allosteric regulations. This implies that the FBPase cannot have a single binding site for its transition to the inactive state (a minimum of two or three binding sites is necessary). Given the multimeric structure of this enzyme, this kinetic hypothesis is tenable. Other possible applications of the stochastic automata approach for different cases of channels, receptors and enzymatic control are suggested.     

Bi-directional replication and random termination

Two-dimensional (2D) agarose gel electrophoresis was used to study termination of DNA replication in a shuttle vector, YRp7′, when it replicated in Escherichia coli, Saccharomyces cerevisiae and Xenopus egg extracts. In E.coli, the 2D gel patterns obtained were consistent with uni-directional replication initiated at a specific site, the ColE1 origin. In consequence, termination also occurred precisely at the ColE1 origin. In Xenopus egg extracts, the particular shape of the bubble arc as well as the triangular smear detected to the left of the simple-Y pattern indicated random initiation and termination. In S.cerevisiae, initiation occurred at the ARS1 origin and replication proceeded in a bi-directional manner. However, termination did not always occur at a specific site 180° across from the origin, but almost all along the south hemisphere of the plasmid. Inversion, deletion or replacement of DNA sequences located throughout this hemisphere did not eliminate random termination. Analysis of the replication intermediates of another yeast plasmid bearing a different origin, ARS305, also exhibited random termination. We propose that the random termination events observed in S.cerevisiae could be due to an asynchronous departure of both forks from the bi-directional origin in addition to differences in the rate of fork progression. These observations could be extended to all bi-directional origins.     

Flavonol glycosides from Asplenium foreziense and its five related taxa and A. incisum

The flavonoids of Asplenium foreziense, A. fontanum subsp. fontanum and subsp. pseudofontanum, A. obovatum subsp. obovatum var. obovatum and var. protobillotii, A. obovatum subsp. lanceolatum, and A. incisum were isolated and identified for chemotaxonomic survey. A major constituent of all taxa was kaempferol 3-O-gentiobioside. As minor compounds, kaempferol 3,7-O-glycoside and/or kaempferol 3-O-glycoside were found in A. fontanum, A. obovatum and A. foreziense, and kaempferol 3-O-gentiobioside-4'-O-glucoside, kaempferol 3-O-glucoside and quercetin 3-O-diglucoside in A. incisum. It was suggested that A. foreziense, A. fontanum including subsp. pseudofontanum and A. obovatum including subsp. lanceolatum are not only morphologically but also chemotaxonomically related. The East Asian A. incisum was chemically and geographically different from these taxa.     

MODBASE, a database of annotated comparative protein structure models

MODBASE is a queryable database of annotated comparative protein structure models. The models are derived by MODPIPE, an automated modeling pipeline relying on the programs PSI-BLAST and MODELLER. The database currently contains 3D models for substantial portions of approximately 17 000 proteins from 10 complete genomes, including those of Caenorhabditis elegans, Saccharomyces cerevisiae and Escherichia coli, as well as all the available sequences from Arabidopsis thaliana and Homo sapiens. The database also includes fold assignments and alignments on which the models were based. In addition, special care is taken to assess the quality of the models. ModBase is accessible through a web interface at http://guitar.rockefeller.edu/modbase/     

Spontaneous c-Fos rhythm in the rat suprachiasmatic nucleus: location and effect of photoperiod

A recently reported circadian rhythm in the spontaneous c-Fos immunoreactivity in the rat suprachiasmatic nucleus (SCN) is expressed mostly in the dorsomedial (dm) SCN, where vasopressinergic cells are located. The aim of the present study is to find out whether day length, i.e., photoperiod, affects the dm-SCN rhythm and, if so, how the rhythm adjusts to a change from a long to a short photoperiod. In addition, a question of whether the spontaneous c-Fos production is localized in vasopressin- producing cells or in other cells is also studied to characterize further the dm-SCN rhythmicity. Combined immunostaining for c-Fos and arginine vasopressin (AVP) revealed that most of c-Fos immunopositive cells were devoid of AVP; the results suggest that c-Fos-producing cells in the dm-SCN are mostly not identical with those producing AVP. In rats maintained under a long photoperiod with 16:8-h light-dark cycle (LD 16:8) daily and then released into darkness, the time of the afternoon and evening decline of the spontaneous c-Fos immunoreactivity in the dm-SCN differed just slightly from the time in rats maintained originally under a short LD 8:16 photoperiod; however, the morning c-Fos rise occurred about 4 h earlier under the long than under the short photoperiod. After a change from a long to a short photoperiod, a rough but not yet a fine adjustment of the morning c-Fos rise to the change was accomplished within 3-6 days. The results show that similar to the recently reported ventrolateral SCN rhythmicity, the intrinsic dm-SCN rhythmicity is also affected by the photoperiod and suggest that the whole SCN state is photoperiod dependent.     

Stroke volume during exercise: interaction of environment and hydration

Euhydrated and dehydrated subjects exercised in a hot and a cold environment with our aim to identify factors that relate to reductions in stroke volume (SV). We hypothesized that reductions in SV with heat stress are related to the interaction of several factors rather than the effect of elevated skin blood flow. Eight male endurance-trained cyclists [maximal O(2) consumption (VO(2 max)) 4.5 +/- 0.1 l/min; means +/- SE] cycled for 30 min (72% VO(2 max)) in the heat (H; 35 degrees C) or the cold (C; 8 degrees C) when euhydrated or dehydrated by 1.5, 3.0, or 4.2% of their body weight. When euhydrated, SV and esophageal temperature (T(es) 38. 2-38.3 degrees C) were similar in H and C, whereas skin blood flow was much higher in H vs. C (365 +/- 64% higher; P < 0.05). With each 1% body weight loss, SV declined 6.4 +/- 1.3 ml (4.8%) in H and 3.4 +/- 0.4 ml (2.5%) in C, whereas T(es) increased 0.21 +/- 0.02 and 0. 10 +/- 0.02 degrees C in H and C, respectively (P < 0.05). However, reductions in SV were not associated with increases in skin blood flow. The reduced SV was highly associated with increased heart rate and reduced blood volume in both H (R = 0.96; P < 0.01) and C (R = 0. 85; P < 0.01). In conclusion, these results suggest that SV is maintained in trained subjects during exercise in euhydrated conditions despite large differences in skin blood flow. Furthermore, the lowering of SV with dehydration appears largely related to increases in heart rate and reductions in blood volume.     

Anticipatory changes in liver metabolism and entrainment of insulin, glucagon, and corticosterone in food-restricted rats

Restricted feeding schedules entrain behavioral and physiological circadian rhythms, which depend on a food-entrainable oscillator (FEO). The mechanism of the FEO might depend on digestive and endocrine processes regulating energy balance. The present study characterizes the dynamics of circulating corticosterone, insulin, and glucagon and regulatory parameters of liver metabolism in rats under restricted feeding schedules. With respect to ad libitum controls, food-restricted rats showed 1) an increase in corticosterone and glucagon and a decrease in insulin before food access, indicating a predominant catabolic state; and 2) a reduction in lactate-to-pyruvate and beta-hydroxybutyrate-to-acetoacetate ratios, indicating an oxidized cytoplasmic and mitochondrial redox state in the liver metabolism. All these changes were reversed after feeding. Moreover, liver energy charge in food-restricted rats did not show a significant modification before feeding, despite an increase in adenine nucleotides, but showed an important decrease after food intake. Variations detected in the liver of food-restricted rats are different from those prevailing under 24-h fasting. These observations suggest "anticipatory activity" of the liver metabolism to optimize the processing of nutrients to daily feeding. Data also suggest a possible relationship of the liver and endocrine signals with the FEO.