Influence of glutethimide on rat brain mononucleotides by sub-chronic codeine treatment

It was investigated the in vivo effect of glutethimide on the intracellular neuroadaptation characteristic for μ-opioid receptor tolerance induced by chronic codeine treatment and reflected by increased levels of adenylyl cyclase (AC) and cAMP-dependent protein kinase (PKA). AC activity was appreciated by cyclic-AMP (cAMP) formation, the levels of adenine and guanine nucleotides in brain extracts being assayed using a high performance liquid chromatographic method. The concomitant chronic administration of codeine and glutethimide resulted in a pronounced and long-lasting energetic depletion of the neurons, consistent with the high risk of overdose, and increase of cAMP's stable metabolite, 5'-AMP. This increase is persistent even after withdrawal and suggests an interference with the adenylyl cyclase system involved in the development of tolerance of opioid receptor and in relapse and provides a possible explanation of addiction and fast increase of doses observed in humans abusing this combination.     

Association of immunological disorders in lethal side effect of NSAIDs on beta-glucan-administered mice

(1-->3)-beta-D-Glucan (beta-glucan) is a biological response modifier that regulates host immune response. We have found that the combination of a beta-glucan and a non-steroidal anti-inflammatory drug (NSAID), indomethacin (IND), induced lethal toxicity in mice [Yoshioka et al. (1998) FEMS Immunol. Med. Microbiol., 21, 171-179]. This study was undertaken to analyze the mechanism of the lethal side effect. Combination of a beta-glucan and IND increased the number of leukocytes, especially macrophages and neutrophils, in various organs and these cells were activated. The activated state of these cells was supported by the enhanced production of interferon-gamma in the presence of IND in vitro culture of the peritoneal exudate cells. Intestinal bacterial flora was translocated into the peritoneal cavity in these mice to cause peritonitis. Comparing the toxicity of various NSAIDs, nabumetone, a partially cyclooxygenase-2-selective NSAID with weaker toxicity to the gastrointestinal tract, did not exhibit a lethal side effect. These facts strongly suggested that gastrointestinal damage by NSAIDs was more severe in beta-glucan-administered mice, resulting in peritonitis by enteric bacteria and leading to death.     

Ecological consequences of the phylogenetic and physiological diversities of acetogens

Acetogens reduce CO₂ to acetate via the acetyl-CoA pathway and have been classically thought of as obligately anaerobic bacteria. Nearly 100 acetogenic species from 20 different genera have been isolated to date. These isolates are able to use very diverse electron donors and acceptors, and it is thus very likely that the in situ activities of acetogens are very diverse and not restricted to acetogenesis. Since acetogens constitute a very phylogenetically diverse bacteriological group, it should be anticipated that they can inhabit, and have impact on, diverse habitats. Indeed, they have been isolated from a broad range of habitats, including oxic soils and other habitats not generally regarded as suitable for acetogens. Although the ecological impact of acetogens is determined by the in situ manifestation of their physiological potentials, assessing their in situ activities is difficult due to their physiological and phylogenetic diversities. This mini-review will highlight a few of the physiological and ecological realities of acetogens, and will focus on: (i) metabolic diversities and regulation, (ii) phylogenetic diversity and molecular ecology, and (iii) the capacity of acetogens to cope with oxic conditions under both laboratory and in situ conditions. This revised version was published online in August 2006 with corrections to the Cover Date.     

A novel short neurotoxin,cobrotoxin c,from monocellate cobra (Naja kaouthia) venom: isolation and purification,primary and secondary structure determination,and tertiary structure modeling

A novel short neurotoxin, cobrotoxin c (CBT C) was isolated from the venom of monocellate cobra (Naja kaouthia) using a combination of ion-exchange chromatography and FPLC. Its primary structure was determined by Edman degradation. CBT C is composed of 61 amino acid residues. It differs from cobrotoxin b (CBT B) by only two amino acid substitutions, Thr/Ala11 and Arg/Thr56, which are not located on the functionally important regions by sequence similarity. However, the LD50 is 0.08 mg/g to mice, i.e. approximately five-fold higher than for CBT B. Strikingly, a structure-function relationship analysis suggests the existence of a functionally important domain on the outside of Loop III of CBT C. The functionally important basic residues on the outside of Loop III might have a pairwise interaction with alpha subunit, instead of gamma or delta subunits of the nicotinic acetylcholine receptor (nAChR).     

Aluminum neurotoxicity is reduced by dantrolene and dimethyl sulfoxide in cultured rat hippocampal neurons

Cell death was reduced in cultured rat hippocampal cells treated with aluminum chloride by dantrolene and dimethylsulfoxide, indicating aluminum toxicity may be mediated through release of calcium from intracellular stores and oxidative stress. Cell death was reduced to a lesser degree by cycloheximide and actinomycin D, indicating some evidence for apoptosis, however apoptosis did not appear to be a major cause of cell death from aluminum toxicity.     

`Every dogma has its day'*: a personal look at carbon metabolism in photosynthetic bacteria

Dogmas are unscientific. What is perhaps the greatest biological dogma of all time, the `unity of biochemistry' is, in the main, still having its day. According to present knowledge, the exceptions to this dogma are mere details when seen in relation to the biosystem as a whole. Nevertheless the exceptions are scientifically interesting and the understanding of them has led to a better comprehension of photosynthesis and ecology. Until the discovery of ¹⁴C, photosynthetic CO₂ fixation was like a slightly opened black box. With ¹⁴C in hand scientists mapped out the path of carbon in green plant photosynthesis in the course of a few years. The impressive reductive pentose phosphate cycle was almost immediately assumed to be universal in autotrophs, including anoxygenic phototrophs, in spite of the odd observation to the contrary. A new dogma was born and held the field for about two decades. Events began to turn when green sulfur bacteria were found to contain ferredoxin-coupled ketoacid-oxidoreductases. This led to the formulation of a novel CO₂-fixing pathway, the reductive citric acid cycle, but its general acceptance required much work by many investigators. However, the ice had now been broken and after some years a third mechanism of CO₂ fixation was discovered, this time in Chloroflexus, and then a fourth in the same genus. One consequence of these discoveries is that it has become apparent that oxygen is an important factor that determines the kind of CO₂-fixing mechanism an organism uses. With the prospect of the characterization of hordes of novel bacteria forecast by molecular ecologists we can expect further distinctive CO₂ fixation mechanisms to turn up. This revised version was published online in August 2006 with corrections to the Cover Date.     

Dose- and time-dependent effects of a novel (−)-hydroxycitric acid extract on body weight,hepatic and testicular lipid peroxidation,DNA fragmentation and histopathological data over a period of 90 days

(–)-Hydroxycitric acid (HCA), a natural extract from the dried fruit rind of Garcinia cambogia (family Guttiferae), is a popular supplement for weight management. The dried fruit rind has been used for centuries as a condiment in Southeastern Asia to make food more filling and satisfying. A significant number of studies highlight the efficacy of Super CitriMax (HCA-SX, a novel 60% calcium-potassium salt of HCA derived from Garcinia cambogia) in weight management. These studies also demonstrate that HCA-SX promotes fat oxidation, inhibits ATP-citrate lyase (a building block for fat synthesis), and lowers the level of leptin in obese subjects. Acute oral, acute dermal, primary dermal irritation and primary eye irritation toxicity studies have demonstrated the safety of HCA-SX. However, no long-term safety of HCA-SX or any other (–)-hydroxycitric acid extract has been previously assessed. In this study, we have evaluated the dose- and time-dependent effects of HCA-SX in Sprague-Dawley rats on body weight, hepatic and testicular lipid peroxidation, DNA fragmentation, liver and testis weight, expressed as such and as a % of body weight and brain weight, and histopathological changes over a period of 90 days. The animals were treated with 0, 0.2, 2.0 and 5.0% HCA-SX as feed intake and the animals were sacrificed on 30, 60 or 90 days of treatment. The feed and water intake were assessed and correlated with the reduction in body weight. HCA-SX supplementation demonstrated a reduction in body weight in both male and female rats over a period of 90 days as compared to the corresponding control animals. An advancing age-induced marginal increase in hepatic lipid peroxidation was observed in both male and female rats as compared to the corresponding control animals. However, no such difference in hepatic DNA fragmentation and testicular lipid peroxidation and DNA fragmentation was observed. Furthermore, liver and testis weight, expressed as such and as a percentage of body weight and brain weight, at 30, 60 and 90 days of treatment, exhibited no significant difference between the four groups. Taken together, these results indicate that treatment of HCA-SX over a period of 90 days results in a reduction in body weight, but did not cause any changes in hepatic and testicular lipid peroxidation, DNA fragmentation, or histopathological changes.     

Characterization of sarcolemma and sarcoplasmic reticulum isolated from skeletal muscle of the freeze tolerant wood frog, Rana sylvatica: the beta(2)-adrenergic receptor and calcium transport systems in control, frozen and thawed states

In freeze tolerant wood frog Rana sylvatica, the freeze-induced liberation of glucose plays a critical role in survival in response to sub-zero temperature exposure. We have shown that the glycaemic response is linked to selective changes in the expression of hepatic adrenergic receptors through which catecholamines act to produce their hepatic glycogenolytic effects. The purpose of the present study was to determine if skeletal muscle, another catecholamine-sensitive tissue with glycogenolytic potential, displayed similar or different changes. In order to achieve these objectives, skeletal muscle derived from Rana sylvatica was studied in control, frozen and thawed states. In isolated sarcolemmal fractions, freezing effected an 88% decrease in beta(2)-adrenergic receptor expression but was without effect on the calcium pump; while thawing resulted in a recovery of the beta(2)-adrenergic receptor to 60% of control levels and a 2.4-fold increase in calcium transport. In isolated sarcoplasmic reticular fractions, freezing effected a 52% decrease in calcium binding and a 92% decrease in oxalate-stimulated calcium uptake; while thawing elicited partial normalization to control levels to 70% with respect to calcium binding and to 47% with respect to calcium uptake. Freezing and thawing were associated with increases and decreases, receptively, in blood glucose levels but were without effect on skeletal muscle glycogen content. Thus these muscle changes in Rana sylvatica in freezing and thawing are not linked to glycogen breakdown, are different from those previously seen in liver, and may provide a role in recovery of muscle function during thawing by protecting glycogen stores for contraction and maximizing extracellular calcium for excitation-contraction coupling in the frozen state. The involvement of thyroid hormone in triggering these muscle changes is discussed.