This article reports the organ distribution and bioaccumulation of hepatotoxic microcystins (MCs) in freshwater fishes at different trophic levels from the large, shallow, eutrophic Lake Chaohu in September 2003, when there were heavy surface blooms of toxic cyanobacteria. Among all fish, intestines and blood had the highest average content of MC-RR + MC-LR (22.0 and 14.5 microg g(-1) DW, respectively), followed by liver, bile, and kidney (7.77, 6.32, and 5.81 microg g(-1) DW, respectively), whereas muscle had the least (1.81 microg g(-1) DW). MC content in muscle was highest in carnivorous fish (Culter ilishaeformis, 2.22 microg g(-1) DW) and omnivorous fish (Carassius auratus, 1.96 microg g(-1) DW) and was lowest in phytoplanktivorous fish (Hypophthalmichthys molitrix, 1.65 microg g(-1) DW) and herbivorous fish (Parabramis pekinensis 0.660 microg g(-1) DW). However, the amount of MC in the gut of H. molitrix (137 microg g(-1) DW) was more than 20 times that in the other fish (<6.50 microg g(-1) DW). The MCs showed a tendency to accumulate up the food chain, and piscivorous fish at the top of the food chain were at high risk of exposure to MCs in Lake Chaohu. Our study is the first to report MC concentrations in the bile and blood of wild fish. One hundred grams of fish muscle would contain 2.64-49.7 microg of MC-LR equivalent, or about 1.3-25 times the recommended tolerable daily intake of MC-LR by humans, indicating that fish are already severely contaminated by MCs and that the local authorities should warn the public of the risk of poisoning by eating the contaminated fish.

Context:The biological basis for the development of major depressive disorder (MDD) remains incompletely understood.Objective: To quantify brain serotonin (5-hydroxytryptamine ) turnover in patients with MDD.Design: Patients with depression were studied both untreated and during administration of a selective serotonin reuptake inhibitor (SSRI) in an unblinded study of sequential design. Healthy volunteers were examined on only 1 occasion. Direct internal jugular venous blood sampling was used to directly quantify brain serotonin turnover. The effect of serotonin transporter (5-HTT) genotype on brain serotonin turnover was evaluated and the influence of SSRI therapy on serotonin turnover was investigated.Setting: Participants were recruited from the general community following media advertisement. Experimental procedures were performed in the research catheterization laboratory of a major training hospital and medical research institute. Conclusions: Brain serotonin turnover is elevated in unmedicated patients with MDD and is influenced by the 5-HTT genotype. The marked reduction in serotonin turnover following SSRI treatment and the accompanying improvement in symptoms suggest that high brain serotonin turnover may be a biological substrate of MDD. Psychiatry. 2008;65(1):38-46 T HE ETIOLOGY OF MAJOR DEpressive disorder (MDD) has been linked to brain monoaminergic neuronal dysfunction. Arch Gen1,2 Of particular interest is the role of brain serotonin (5-hydroxytryptamine [5-HT]) in MDD. The diversity of roles played by serotonin coupled with the lack of a demonstrated relationship between different clinical presentations and biochemical abnormalities has hampered the development of sensitive markers of the disease. Indeed, brain serotonin-releasing neurons subserve diverse although incompletely understood functions related to emotions and behavior, feeding and adiposity, 3 and light stimulation. 4 We have previously demonstrated influences of obesity and feeding 5 and season and sunlight 6 on brain serotonin turnover in humans. The principal means of intraneuronal metabolism of serotonin is via oxidative deamination by monoamine oxidase resulting in formation of 5-hydroxyindoleacetic acid (5-HIAA) (Figure 1). Deamination followed by reduction, conjugation with sulfate or glucuronide, and

1. In searching for biological evidence that essential hypertension is caused by chronic mental stress, a disputed proposition, parallels are noted with panic disorder, which provides an explicit clinical model of recurring stress responses. 2. There is clinical comorbidity; panic disorder prevalence is increased threefold in essential hypertension. Plasma cortisol is elevated in both. 3. In panic disorder and essential hypertension, but not in health, single sympathetic nerve fibres commonly fire repeatedly within an individual cardiac cycle; this appears to be a signature of stress exposure. For both conditions, adrenaline cotransmission is present in sympathetic nerves. 4. Tissue nerve growth factor is increased in both (nerve growth factor is a stress reactant). There is induction of the adrenaline synthesizing enzyme, phenylethanolamine-N-methyltransferase, in sympathetic nerves, an explicit indicator of mental stress exposure. 5. The question of whether chronic mental stress causes high blood pressure, still hotly debated, has been reviewed by an Australian Government body, the Specialist Medical Review Council. Despite the challenging medicolegal implications, the Council determined that stress is one proven cause of hypertension, this ruling being published in the 27 March 2002 Australian Government Gazette. This judgement was reached after consideration of the epidemiological evidence, but in particular after review of the specific elements of the neural pathophysiology of essential hypertension, described above.

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SUMMARY1. Trait-based approaches provide a framework for integrating the distribution of functional traits associated with ecological strategies into the responses of plant community dynamics along environmental gradients. We used a trait-based approach to unravel the processes governing macrophyte community assembly along a water depth gradient. We sampled 42 plots and 1513 individual plants and measured 12 functional traits and abundance of 17 macrophyte species. 2. The results showed significant evidences of habitat filtering (i.e. a significant reduction in the range and variance of trait values) and of niche differentiation (i.e. trait values distributed more evenly than expected), both of which affected the functional responses of macrophyte communities associated with different sets of traits in significant different patterns along the gradient. 3. Habitat filtering effects increased significantly for specific leaf area and leaf carbon content along the gradient. Niche differentiation effects increased significantly for leaf dry mass content, but decreased for ramet size, shoot height and leaf carbon content with increasing water depth, implying that the relative strength of biotic competition in a specific functional niche would vary with water depth. 4. Intraspecific trait variability promoted significantly the detection of habitat filtering effects on stem diameter, lamina thickness and stem dry mass content, and niche differentiation effects on specific leaf area, leaf dry mass content, shoot height, stem diameter, stem dry mass content and ramet size. 5. Community assembly processes shape the functional trait distribution within communities along environmental gradients through hierarchical effects of habitat filtering and niche differentiation. Our study highlights that niche differentiation plays a structuring role in macrophyte community assembly and that intraspecific trait variability is an important factor influencing macrophyte community dynamics.

Panic disorder can serve as a clinical model for testing whether mental stress can cause heart disease. Potential neural mechanisms of cardiac risk are the sympathetic activation during panic attacks, continuing release of adrenaline as a co-transmitter in the cardiac sympathetic nerves, and impairment of noradrenaline neuronal reuptake, augmenting sympathetic neural respnses. The phenotype of impaired neuronal reuptake of noradrenaline: an epigenetic mechanism? We suspect that this phenotype, in sensitizing people to heart symptom development, is a cause of panic disorder, and by magnifying the sympathetic neural signal in the heart, underlies increased cardiac risk. No loss of function mutations of the coding region of the norepinephrine transporter (NET) are evident, but we do detect hypermethylation of CpG islands in the NET gene promoter region. Chromatin immunoprecipitation methodology demonstrates binding of the inhibitory transcription factor, MeCP2, to promoter region DNA in panic disorder patients. Cardiovascular illnesses co-morbid with panic disorder. Panic disorder commonly coexists with essential hypertension and the postural tachycardia syndrome. In both of these cardiovascular disorders the impaired neuronal noradrenaline reuptake phenotype is also present and, as with panic disorder, is associated with NET gene promoter region DNA hypermethylation. An epigenetic 'co-morbidity' perhaps underlies the clinical concordance. Brain neurotransmitters. Using internal jugular venous sampling, in the absence of a panic attack we find normal norepinephrine turnover, but based on measurements of the overflow of the serotonin metabolite, 5HIAA, a marked increase (six to sevenfold) in brain serotonin turnover in patients with panic disorder. This appears to represent the underlying neurotransmitter substrate for the disorder. Whether this brain serotonergic activation is a prime mover, or consequential on other primary causes of panic disorder, including cardiac sensitization by faulty neuronal noradrenaline reuptake leading to cardiac symptoms and the enhanced vigilance which accompanies them, is unclear at present.

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Objective— The postural tachycardia syndrome (POTS) has multiple symptoms, chief among which are tachycardia, weakness, and recurrent blackouts while standing. Previous research has implicated dysfunction of the norepinephrine transporter. A coding mutation in the norepinephrine transporter gene ( SLC6A2 ) sequence has been reported in 1 family kindred only. The goal of the present study was to further characterize the role and regulation of the SLC6A2 gene in POTS. Methods and Results— Sympathetic nervous system responses to head-up tilt were examined by combining norepinephrine plasma kinetics measurements and muscle sympathetic nerve activity recordings in patients with POTS compared with that in controls. The SLC6A2 gene sequence was investigated in leukocytes from POTS patients and healthy controls using single nucleotide polymorphisms genotyping, bisulphite sequencing, and chromatin immunoprecipitation assays for histone modifications and binding of the transcriptional regulatory complex, methyl-CpG binding protein 2. The expression of norepinephrine transporter was lower in POTS patients compared with healthy volunteers. In the absence of altered SLC6A2 gene sequence or promoter methylation, this reduced expression was directly correlated with chromatin modifications. Conclusion— We propose that chromatin-modifying events associated with SLC6A2 gene suppression may constitute a mechanism of POTS.