The Gene Ontology (GO) database and informatics resource

The Gene Ontology (GO) project (http://www. geneontology.org/) provides structured, controlled vocabularies and classifications that cover several domains of molecular and cellular biology and are freely available for community use in the annotation of genes, gene products and sequences. Many model organism databases and genome annotation groups use the GO and contribute their annotation sets to the GO resource. The GO database integrates the vocabularies and contributed annotations and provides full access to this information in several formats. Members of the GO Consortium continually work collectively, involving outside experts as needed, to expand and update the GO vocabularies. The GO Web resource also provides access to extensive documentation about the GO project and links to applications that use GO data for functional analyses.

Mitochondrial complex I deficiency in Parkinson's disease

The structure and function of mitochondrial respiratory-chain enzyme proteins were studied postmortem in the substantia nigra of nine patients with Parkinson's disease and nine matched controls. Total protein and mitochondrial mass were similar in the two groups. NADH-ubiquinone reductase (Complex I) and NADH cytochrome c reductase activities were significantly reduced, whereas succinate cytochrome c reductase activity was normal. These results indicated a specific defect of Complex I activity in the substantia nigra of patients with Parkinson's disease. This biochemical defect is the same as that produced in animal models of parkinsonism by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and adds further support to the proposition that Parkinson's disease may be due to an environmental toxin with action(s) similar to those of MPTP.

Interactive memory systems in the human brain

Learning and memory in humans rely upon several memory systems, which appear to have dissociable brain substrates. A fundamental question concerns whether, and how, these memory systems interact. Here we show using functional magnetic resonance imaging (FMRI) that these memory systems may compete with each other during classification learning in humans. The medial temporal lobe and basal ganglia were differently engaged across subjects during classification learning depending upon whether the task emphasized declarative or nondeclarative memory, even when the to-be-learned material and the level of performance did not differ. Consistent with competition between memory systems suggested by animal studies and neuroimaging, activity in these regions was negatively correlated across individuals. Further examination of classification learning using event-related FMRI showed rapid modulation of activity in these regions at the beginning of learning, suggesting that subjects relied upon the medial temporal lobe early in learning. However, this dependence rapidly declined with training, as predicted by previous computational models of associative learning.

Recovering meaning: left prefrontal cortex guides controlled semantic retrieval

Prefrontal cortex plays a central role in mnemonic control, with left inferior prefrontal cortex (LIPC) mediating control of semantic knowledge. One prominent theory posits that LIPC does not mediate semantic retrieval per se, but rather subserves the selection of task-relevant knowledge from amidst competing knowledge. The present event-related fMRI study provides evidence for an alternative hypothesis: LIPC guides controlled semantic retrieval irrespective of whether retrieval requires selection against competing representations. With selection demands held constant, LIPC activation increased with semantic retrieval demands and with the level of control required during retrieval. LIPC mediates a top-down bias signal that is recruited to the extent that the recovery of meaning demands controlled retrieval. Selection may reflect a specific instantiation of this mechanism.

Mutations in Kir2.1 Cause the Developmental and Episodic Electrical Phenotypes of Andersen's Syndrome

Andersen's syndrome is characterized by periodic paralysis, cardiac arrhythmias, and dysmorphic features. We have mapped an Andersen's locus to chromosome 17q23 near the inward rectifying potassium channel gene KCNJ2. A missense mutation in KCNJ2 (encoding D71V) was identified in the linked family. Eight additional mutations were identified in unrelated patients. Expression of two of these mutations in Xenopus oocytes revealed loss of function and a dominant negative effect in Kir2.1 current as assayed by voltage-clamp. We conclude that mutations in Kir2.1 cause Andersen's syndrome. These findings suggest that Kir2.1 plays an important role in developmental signaling in addition to its previously recognized function in controlling cell excitability in skeletal muscle and heart.

Identification of novel genes, SYT and SSX, involved in the t(X;18)(p11.2;q11.2) translocation found in human synovial sarcoma

Human synovial sarcomas contain a recurrent and specific chromosomal translocation t(X;18)(p11.2;q11.2). By screening a synovial sarcoma cDNA library with a yeast artificial chromosome spanning the X chromosome breakpoint, we have identified a hybrid transcript that contains 5' sequences (designated SYT) mapping to chromosome 18 and 3' sequences (designated SSX) mapping to chromosome X. An SYT probe detected genomic rearrangements in 10/13 synovial sarcomas. Sequencing of cDNA clones shows that the normal SYT gene encodes a protein rich in glutamine, proline and glycine, and indicates that in synovial sarcoma rearrangement of the SYT gene results in the formation of an SYT-SSX fusion protein. Both SYT and SSX failed to exhibit significant homology to known gene sequences.

Anatomic and disease specificity of NADH CoQ1 reductase (complex I) deficiency in Parkinson's disease

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) is thought to produce parkinsonism in humans and other primates through its inhibition of complex I. The recent discovery of mitochondrial complex I deficiency in the substantia nigra of patients with Parkinson's disease has provided a remarkable link between the idiopathic disease and the action of the neurotoxin MPTP. This article shows that complex I deficiency in Parkinson's disease is anatomically specific for the substantia nigra, and is not present in another neurodegenerative disorder involving the substantia nigra. Evidence is also provided to show that there is no correlation between L-3,4-dihydroxyphenylalanine therapy and complex I deficiency. These results suggest that complex I deficiency may be the underlying cause of dopaminergic cell death in Parkinson's disease.

A prospective, randomized, double-blind comparison of bilateral and right unilateral electroconvulsive therapy at different stimulus intensities

BACKGROUND

Controversy persists about the use of right unilateral (RUL) and bilateral (BL) electroconvulsive therapy (ECT). While RUL ECT results in less severe short-term and long-term cognitive effects, there is concern that it is less efficacious than BL ECT.

METHODS

In a double-blind study, 80 depressed patients were randomized to RULECT, with electrical dosages 50%, 150%, or 500% above the seizure threshold, or BL ECT, with an electrical dosage 150% above the threshold. Depression severity and cognitive functioning were assessed before, during, immediately after, and 2 months after ECT. Compared with baseline, responders had at least a 60% reduction in symptom scores 1 week after ECT, and were monitored for relapse for 1 year.

RESULTS

High-dosage RUL and BL ECT were equivalent in response rate (65%) and approximately twice as effective as low-dosage (35%) or moderate-dosage (30%) unilateral ECT. During the week after the randomized phase, BL ECT resulted in greater impairment than any dosage of unilateral ECT in several measures of anterograde and retrograde memory. Two months after ECT, retrograde amnestic deficits were greatest among patients treated with BL ECT. Thirty-three (53%) of the 62 patients who responded to ECT relapsed, without treatment group differences. The relapse rate was greater in patients who had not responded to adequate pharmacotherapy prior to ECT and who had more severe depressive symptoms after ECT.

CONCLUSION

Right unilateral ECT at high dosage is as effective as a robust form of BL ECT, but produces less severe and persistent cognitive effects.

Interactions of mast cell tryptase with thrombin receptors and PAR-2

Tryptase is a serine protease secreted by mast cells that is able to activate other cells. In the present studies we have tested whether these responses could be mediated by thrombin receptors or PAR-2, two G-protein-coupled receptors that are activated by proteolysis. When added to a peptide corresponding to the N terminus of PAR-2, tryptase cleaved the peptide at the activating site, but at higher concentrations it also cleaved downstream, as did trypsin, a known activator of PAR-2. Thrombin, factor Xa, plasmin, urokinase, plasma kallikrein, and tissue kallikrein had no effect. Tryptase also cleaved the analogous thrombin receptor peptide at the activating site but less efficiently. When added to COS-1 cells expressing either receptor, tryptase stimulated phosphoinositide hydrolysis. With PAR-2, this response was half-maximal at 1 nM tryptase and could be inhibited by the tryptase inhibitor, APC366, or by antibodies to tryptase and PAR-2. When added to human endothelial cells, which normally express PAR-2 and thrombin receptors, or keratinocytes, which express only PAR-2, tryptase caused an increase in cytosolic Ca2+. However, when added to platelets or CHRF-288 cells, which express thrombin receptors but not PAR-2, tryptase caused neither aggregation nor increased Ca2+. These results show that 1) tryptase has the potential to activate both PAR-2 and thrombin receptors; 2) for PAR-2, this potential is realized, although cleavage at secondary sites may limit activation, particularly at higher tryptase concentrations; and 3) in contrast, although tryptase clearly activates thrombin receptors in COS-1 cells, it does not appear to cleave endogenous thrombin receptors in platelets or CHRF-288 cells. These distinctions correlate with the observed differences in the rate of cleavage of the PAR-2 and thrombin receptor peptides by tryptase. Tryptase is the first protease other than trypsin that has been shown to activate human PAR-2. Its presence within mast cell granules places it in tissues where PAR-2 is expressed but trypsin is unlikely to reach.

The amino-terminal domain of heat shock protein 90 (hsp90) that binds geldanamycin is an ATP/ADP switch domain that regulates hsp90 conformation

Many functions of the chaperone, heat shock protein 90 (hsp90), are inhibited by the drug geldanamycin that specifically binds hsp90. We have studied an amino-terminal domain of hsp90 whose crystal structure has recently been solved and determined to contain a geldanamycin-binding site. We demonstrate that, in solution, drug binding is exclusive to this domain. This domain also binds ATP linked to Sepharose through the gamma-phosphate. Binding is specific for ATP and ADP and is inhibited by geldanamycin. Mutation of four glycine residues within two proposed ATP binding motifs diminishes both geldanamycin binding and the ATP-dependent conversion of hsp90 to a conformation capable of binding the co-chaperone p23. Since p23 binding requires regions outside the 1-221 domain of hsp90, these results indicate a common site for nucleotides and geldanamycin that regulates the conformation of other hsp90 domains.

Health-related quality of life in patients served by the Department of Veterans Affairs: results from the Veterans Health Study

BACKGROUND

The Department of Veterans Affairs Health Care System (VA) is the largest integrated single payer system in the United States. To date, there has been no systematic measurement of health status in the VA. The Veterans Health Study has developed methods to assess patient-based health status in ambulatory populations.

OBJECTIVES

To describe the health status of veterans and examine the relationships between their health-related quality of life, age, comorbidity, and socioeconomic and service-connected disability status.

METHODS

Participants in the Veterans Health Study, a 2-year longitudinal study, were recruited from a representative sample of patients receiving ambulatory care at 4 VA facilities in the New England region. The Veterans Health Study patients received questionnaires of health status, including the Medical Outcomes Study Short Form 36-Item Health Survey; and a health examination, clinical assessments, and medical history taking. Sixteen hundred sixty-seven patients for whom we conducted baseline assessments are described.

RESULTS

The VA outpatients had poor health status scores across all measures of the Medical Outcomes Study Short Form 36-Item Health Survey compared with scores in non-VA populations (at least 50% of 1 SD worse). Striking differences also were found with the sample stratified by age group (20-49 years, 50-64 years, and 65-90 years). For 7 of the 8 scales (role limitations due to physical problems, bodily pain, general health perceptions, vitality, social functioning, role limitations due to emotional problems, and mental health), scores were considerably lower among the younger patients; for the eighth scale (physical function), scores of the young veterans (aged 20-49 years) were almost comparable with the levels in the old veterans (>65 years). The mental health scores of young veterans were substantially worse than all other age groups (P<.001) and scores of screening measures for depression were significantly higher in the youngest age group (51%) compared with the oldest age groups (33% and 16%) (P<.001).

CONCLUSIONS

The VA outpatients have substantially worse health status than non-VA populations. Mental health differences between the young and old veterans who use the VA health care system are sharply contrasting; the young veterans are sicker, suggesting substantially higher resource needs. Mental health differences may explain much of the worse health-related quality of life in young veterans. As health care systems continue to undergo a radical transformation, the Department of Veterans Affairs should focus on the provision of mental health services for its younger veteran.

Role of apoptosis in failure of beta-cell mass compensation for insulin resistance and beta-cell defects in the male Zucker diabetic fatty rat

To define the mechanisms involved in the evolution of diabetes in the Zucker diabetic fatty (ZDF) rat, beta-cell mass and replication rates were determined by immunochemistry, point-counting morphometry, and 6-h 5-bromo-2'-deoxyuridine (BrdU) incorporation. The beta-cell mass in 5- to 7-week-old prediabetic ZDF rats (4.3 +/- 0.06 mg) was similar to age-matched insulin-resistant Zucker fatty (ZF) rats (3.7 +/- 0.05 mg) and greater than that in Zucker lean control (ZLC) rats (1.9 +/- 0.3, P < 0.05). At 12 weeks (after diabetes onset), beta-cell mass in the ZDF rats (8.1 +/- 1.7 mg) was significantly lower than the ZF rats (15.7 +/- 1.8 mg). The mass in the ZF rats was significantly greater than in the ZLC rats (4.3 +/- 0.8 mg, P < 0.05). The beta-cell proliferation rate (mean of both time points) was significantly greater in the ZDF rats (0.88 +/- 0.1%) compared with the ZF and ZLC rats (0.53 +/- 0.07%, 0.62 +/- 0.07%, respectively, P < 0.05), yet ZDF rats have a lower beta-cell mass than the ZF rats despite a higher proliferative rate. Morphological evidence of neogenesis and apoptosis is evident in the ZF and ZDF rats. In addition, even at 5-7 weeks a modest defect in insulin secretion per beta-cell unit was found by pancreas perfusion. These studies provide evidence that the expansion of beta-cell mass in response to insulin resistance and insulin secretory defects in diabetic ZDF rats is inadequate. This failure of beta-cell mass expansion in the ZDF rat does not appear to be from a reduction in the rate of beta-cell proliferation or neogenesis, suggesting an increased rate of cell death by apoptosis.

A rapid method for the preparation of relatively pure metabolically competent synaptosomes from rat brain

A rapid (less than 2h) method is described for the preparation of synaptosomes from rat brain by using a discontinuous Ficoll/sucrose gradient by a flotation technique. These synaptosomes are metabolically active and minimally (less than 5%) contaminated with 'free' mitochondria as judged by marker-enzyme assays and electron microscopy.

Nitric oxide-mediated mitochondrial damage in the brain: mechanisms and implications for neurodegenerative diseases

Within the CNS and under normal conditions, nitric oxide (.NO) appears to be an important physiological signalling molecule. Its ability to increase cyclic GMP concentration suggests that .NO is implicated in the regulation of important metabolic pathways in the brain. Under certain circumstances .NO synthesis may be excessive and .NO may become neurotoxic. Excessive glutamate-receptor stimulation may lead to neuronal death through a mechanism implicating synthesis of both .NO and superoxide (O2.-) and hence peroxynitrite (ONOO-) formation. In response to lipopolysaccharide and cytokines, glial cells may also be induced to synthesize large amounts of .NO, which may be deleterious to the neighbouring neurones and oligodendrocytes. The precise mechanism of .NO neurotoxicity is not fully understood. One possibility is that it may involve neuronal energy deficiency. This may occur by ONOO- interfering with key enzymes of the tricarboxylic acid cycle, the mitochondrial respiratory chain, mitochondrial calcium metabolism, or DNA damage with subsequent activation of the energy-consuming pathway involving poly(ADP-ribose) synthetase. Possible mechanisms whereby ONOO- impairs the mitochondrial respiratory chain and the relevance for neurotoxicity are discussed. The intracellular content of reduced glutathione also appears important in determining the sensitivity of cells to ONOO- production. It is concluded that neurotoxicity elicited by excessive .NO production may be mediated by mitochondrial dysfunction leading to an energy deficiency state.

Effect of peroxynitrite on the mitochondrial respiratory chain: differential susceptibility of neurones and astrocytes in primary culture

The effect of the neurotoxic nitric oxide derivative, the peroxynitrite anion (ONOO-), on the activity of the mitochondrial respiratory chain complexes in cultured neurones and astrocytes was studied. A single exposure of the neurones to ONOO- (initial concentrations of 0.01-2.0 mM) caused, after a subsequent 24-h incubation, a dose-dependent decrease in succinate-cytochrome c reductase (60% at 0.5 mM) and in cytochrome c oxidase (52% at 0.5 mM) activities. NADH-ubiquinone-1 reductase was unaffected. In astrocytes, the activity of the mitochondrial complexes was not affected up to 2 mM ONOO-. Citrate synthase was unaffected in both cell types under all conditions studied. However, lactate dehydrogenase activity released to the culture medium was increased by ONOO- in a dose-dependent manner (40% at 0.5 mM ONOO-) from the neurones but not from the astrocytes. Neuronal glutathione concentration decreased by 39% at 0.1 mM ONOO-, but astrocytic glutathione was not affected up to 2 mM ONOO-. In isolated brain mitochondria, only succinate-cytochrome c reductase activity was affected (22% decrease at 1 mM ONOO-). We conclude that the acute exposure of ONOO- selectively damages neurones, whereas astrocytes remain unaffected. Intracellular glutathione appears to be an important factor for ameliorating ONOO(-)-mediated mitochondrial damage. This study supports the hypothesis that the neurotoxicity of nitric oxide is mediated through mitochondrial dysfunction.

Duplication of the fusion of TMPRSS2 to ERG sequences identifies fatal human prostate cancer

New predictive markers for managing prostate cancer are urgently required because of the highly variable natural history of this disease. At the time of diagnosis, Gleason score provides the gold standard for assessing the aggressiveness of prostate cancer. However, the recent discovery of TMPRSS2 fusions to the ERG gene in prostate cancer raises the possibility of using alterations at the ERG locus as additional mechanism-based prognostic indicators. Fluorescence in situ hybridization (FISH) assays were used to assess ERG gene status in a cohort of 445 prostate cancers from patients who had been conservatively managed. The FISH assays detected separation of 5' (labelled green) and 3' (labelled red) ERG sequences, which is a consequence of the TMPRSS2-ERG fusion, and additionally identify interstitial deletion of genomic sequences between the tandemly located TMPRSS2 and ERG gene sequences on chromosome 21. Cancers lacking ERG alterations exhibited favourable cause-specific survival (90% survival at 8 years). We identify a novel category of prostate cancers, characterized by duplication of the fusion of TMPRSS2 to ERG sequences together with interstitial deletion of sequences 5' to ERG (called '2+Edel'), which by comparison exhibited extremely poor cause-specific survival (hazard ratio=6.10, 95% confidence ratio=3.33-11.15, P<0.001, 25% survival at 8 years). In multivariate analysis, '2+Edel' provided significant prognostic information (P=0.003) in addition to that provided by Gleason score and prostate-specific antigen level at diagnosis. Other individual categories of ERG alteration were associated with intermediate or good prognosis. We conclude that determination of ERG gene status, including duplication of the fusion of TMPRSS2 to ERG sequences in 2+Edel, allows stratification of prostate cancer into distinct survival categories.

Nitric oxide, mitochondria and neurological disease

Damage to the mitochondrial electron transport chain has been suggested to be an important factor in the pathogenesis of a range of neurological disorders, such as Parkinson's disease, Alzheimer's disease, multiple sclerosis, stroke and amyotrophic lateral sclerosis. There is also a growing body of evidence to implicate excessive or inappropriate generation of nitric oxide (NO) in these disorders. It is now well documented that NO and its toxic metabolite, peroxynitrite (ONOO-), can inhibit components of the mitochondrial respiratory chain leading, if damage is severe enough, to a cellular energy deficiency state. Within the brain, the susceptibility of different brain cell types to NO and ONOO- exposure may be dependent on factors such as the intracellular reduced glutathione (GSH) concentration and an ability to increase glycolytic flux in the face of mitochondrial damage. Thus neurones, in contrast to astrocytes, appear particularly vulnerable to the action of these molecules. Following cytokine exposure, astrocytes can increase NO generation, due to de novo synthesis of the inducible form of nitric oxide synthase (NOS). Whilst the NO/ONOO- so formed may not affect astrocyte survival, these molecules may diffuse out to cause mitochondrial damage, and possibly cell death, to other cells, such as neurones, in close proximity. Evidence is now available to support this scenario for neurological disorders, such as multiple sclerosis. In other conditions, such as ischaemia, increased availability of glutamate may lead to an activation of a calcium-dependent nitric oxide synthase associated with neurones. Such increased/inappropriate NO formation may contribute to energy depletion and neuronal cell death. The evidence available for NO/ONOO--mediated mitochondrial damage in various neurological disorders is considered and potential therapeutic strategies are proposed.

Fusion of SYT to two genes, SSX1 and SSX2, encoding proteins with homology to the Kruppel-associated box in human synovial sarcoma

We demonstrate that the cytogenetically defined translocation t(X;18)(p11.2;q11.2) found in human synovial sarcoma results in the fusion of the chromosome 18 SYT gene to either of two distinct genes, SSX1 or SSX2, at Xp11.2. The SSX1 and SSX2 genes encode closely related proteins (81% identity) of 188 amino acids that are rich in charged amino acids. The N-terminal portion of each SSX protein exhibits homology to the Kruppel-associated box (KRAB), a transcriptional repressor domain previously found only in Kruppel-type zinc finger proteins. PCR analysis demonstrates the presence of SYT-SSX1 or SYT-SSX2 fusion transcripts in 29 of 32 of the synovial sarcomas examined, indicating that the detection of these hybrid transcripts by PCR may represent a very useful diagnostic method. Sequence analysis has demonstrated heterogeneity in the fusion transcripts with the formation of two distinct SYT-SSX1 fusion junctions and two distinct SYT-SSX2 fusion junctions.

Beta-amyloid inhibits integrated mitochondrial respiration and key enzyme activities

Disrupted energy metabolism, in particular reduced activity of cytochrome oxidase (EC 1.9.3.1), alpha-ketoglutarate dehydrogenase (EC 1.2.4.2) and pyruvate dehydrogenase (EC 1.2.4.1) have been reported in post-mortem Alzheimer's disease brain. beta-Amyloid is strongly implicated in Alzheimer's pathology and can be formed intracellularly in neurones. We have investigated the possibility that beta-amyloid itself disrupts mitochondrial function. Isolated rat brain mitochondria have been incubated with the beta-amyloid alone or together with nitric oxide, which is known to be elevated in Alzheimer's brain. Mitochondrial respiration, electron transport chain complex activities, alpha-ketoglutarate dehydrogenase activity and pyruvate dehydrogenase activity have been measured. Beta-amyloid caused a significant reduction in state 3 and state 4 mitochondrial respiration that was further diminished by the addition of nitric oxide. Cytochrome oxidase, alpha-ketoglutarate dehydrogenase and pyruvate dehydrogenase activities were inhibited by beta-amyloid. The K(m) of cytochrome oxidase for reduced cytochrome c was raised by beta-amyloid. We conclude that beta-amyloid can directly disrupt mitochondrial function, inhibits key enzymes and may contribute to the deficiency of energy metabolism seen in Alzheimer's disease.

The risk of tuberculosis related to tumour necrosis factor antagonist therapies: a TBNET consensus statement

Anti-tumour necrosis factor (TNF) monoclonal antibodies or soluble TNF receptors have become an invaluable treatment against chronic inflammatory diseases, such as rheumatoid arthritis, inflammatory bowel disease and psoriasis. Individuals who are treated with TNF antagonists are at an increased risk of reactivating latent infections, especially tuberculosis (TB). Following TNF antagonist therapy, the relative risk for TB is increased up to 25 times, depending on the clinical setting and the TNF antagonist used. Interferon-γ release assays or, as an alternative in individuals without a history of bacille Calmette-Guérin vaccination, tuberculin skin testing is recommended to screen all adult candidates for TNF antagonist treatment for the presence of latent infection with Mycobacterium tuberculosis. Moreover, paediatric practice suggests concomitant use of both the tuberculin skin test and an interferon-γ release assay, as there are insufficient data in children to recommend one test over the other. Consequently, targeted preventive chemotherapy is highly recommended for all individuals with persistent M. tuberculosis-specific immune responses undergoing TNF antagonist therapy as it significantly reduces the risk of progression to TB. This TBNET consensus statement summarises current knowledge and expert opinions and provides evidence-based recommendations to reduce the TB risk among candidates for TNF antagonist therapy.

From synapse to vesicle: the reuptake and storage of biogenic amine neurotransmitters

Biogenic amine transport systems in the presynaptic plasma membrane and the synaptic vesicle provide a mechanism for rapidly terminating the action of released transmitters and for recycling neurotransmitters. Alterations in the activity of these transporters, either by endogenous regulatory mechanisms or by drugs, affect the regulation of synaptic transmitter levels. For drugs such as antidepressants and stimulants that interact with these transport systems, the therapeutic and behavioral consequences are profound. Now that the cDNAs encoding the transporters have been isolated, we can expect rapid progress in understanding how the individual proteins work at the molecular level to couple ion gradients to the reuptake and storage of biogenic amine neurotransmitters.

Nitric oxide-mediated inhibition of the mitochondrial respiratory chain in cultured astrocytes

The Ca(2+)-independent form of nitric oxide synthase was induced in rat neonatal astrocytes in primary culture by incubation with lipopolysaccharide (1 microgram/ml) plus interferon-gamma (100 U/ml), and the activities of the mitochondrial respiratory chain components were assessed. Incubation for 18 h produced 25% inhibition of cytochrome c oxidase activity. NADH-ubiquinone-1 reductase (complex I) and succinate-cytochrome c reductase (complex II-III) activities were not affected. Prolonged incubation for 36 h gave rise to a 56% reduction of cytochrome c oxidase activity and a 35% reduction in succinate-cytochrome c reductase activity, but NADH-ubiquinone-1 reductase activity was unchanged. Citrate synthase activity was not affected by any of these conditions. The inhibition of the activities of these mitochondrial respiratory chain complexes was prevented by incubation in the presence of the specific nitric oxide synthase inhibitor NG-monomethyl-L-arginine. The lipopolysaccharide/interferon-gamma treatment of the astrocytes produced an increase in glycolysis and lactate formation. These results suggest that inhibition of the mitochondrial respiratory chain after induction of astrocytic nitric oxide synthase may represent a mechanism for nitric oxide-mediated neurotoxicity.

Dietary phytoestrogens and cancer: in vitro and in vivo studies

Thirty postmenopausal women (11 omnivores, 10 vegetarians and 9 apparently healthy women with surgically removed breast cancer) were investigated with regard to the association of their urinary excretion of estrogens, lignans and isoflavonoids (all diphenols) with plasma sex hormone binding globulin (SHBG). A statistically significant positive correlation between urinary total diphenol excretion and plasma SHBG was found which remained statistically significant after elimination of the confounding effect of body mass determined by body mass index (BMI). Furthermore we found a statistically significant negative correlation between plasma SHBG and urinary excretion of 16 alpha-hydroxyestrone and estriol which also remained significant after eliminating the effect of BMI. Furthermore we observed that enterolactone (Enl) stimulates the synthesis of SHBG by HepG2 liver cancer cells in culture acting synergistically with estradiol and at physiological concentrations. Enl was rapidly conjugated by the liver cells, mainly to its monosulfate. Several lignans and the isoflavonoids daidzein and equol were found to compete with estradiol for binding to the rat uterine type II estrogen binding site (the s.c. bioflavonoid receptor). It is suggested that lignans and isoflavonoids may affect uptake and metabolism of sex hormones by participating in the regulation of plasma SHBG levels and in this way influence their biological activity and that they may inhibit cancer cell growth like some flavonoids by competing with estradiol for the type II estrogen binding sites.