Alterations in metabolic pathways and networks in Alzheimer's disease.

The pathogenic mechanisms of Alzheimer's disease (AD) remain largely unknown and clinical trials have not demonstrated significant benefit. Biochemical characterization of AD and its prodromal phase may provide new diagnostic and therapeutic insights. We used targeted metabolomics platform to profile cerebrospinal fluid (CSF) from AD (n=40), mild cognitive impairment (MCI, n=36) and control (n=38) subjects; univariate and multivariate analyses to define between-group differences; and partial least square-discriminant analysis models to classify diagnostic groups using CSF metabolomic profiles. A partial correlation network was built to link metabolic markers, protein markers and disease severity. AD subjects had elevated methionine (MET), 5-hydroxyindoleacetic acid (5-HIAA), vanillylmandelic acid, xanthosine and glutathione versus controls. MCI subjects had elevated 5-HIAA, MET, hypoxanthine and other metabolites versus controls. Metabolite ratios revealed changes within tryptophan, MET and purine pathways. Initial pathway analyses identified steps in several pathways that appear altered in AD and MCI. A partial correlation network showed total tau most directly related to norepinephrine and purine pathways; amyloid-ß (Ab42) was related directly to an unidentified metabolite and indirectly to 5-HIAA and MET. These findings indicate that MCI and AD are associated with an overlapping pattern of perturbations in tryptophan, tyrosine, MET and purine pathways, and suggest that profound biochemical alterations are linked to abnormal Ab42 and tau metabolism. Metabolomics provides powerful tools to map interlinked biochemical pathway perturbations and study AD as a disease of network failure.

Pharmacometabolomic mapping of early biochemical changes induced by sertraline and placebo.

In this study, we characterized early biochemical changes associated with sertraline and placebo administration and changes associated with a reduction in depressive symptoms in patients with major depressive disorder (MDD). MDD patients received sertraline or placebo in a double-blind 4-week trial; baseline, 1 week, and 4 weeks serum samples were profiled using a gas chromatography time of flight mass spectrometry metabolomics platform. Intermediates of TCA and urea cycles, fatty acids and intermediates of lipid biosynthesis, amino acids, sugars and gut-derived metabolites were changed after 1 and 4 weeks of treatment. Some of the changes were common to the sertraline- and placebo-treated groups. Changes after 4 weeks of treatment in both groups were more extensive. Pathway analysis in the sertraline group suggested an effect of drug on ABC and solute transporters, fatty acid receptors and transporters, G signaling molecules and regulation of lipid metabolism. Correlation between biochemical changes and treatment outcomes in the sertraline group suggested a strong association with changes in levels of branched chain amino acids (BCAAs), lower BCAAs levels correlated with better treatment outcomes; pathway analysis in this group revealed that methionine and tyrosine correlated with BCAAs. Lower levels of lactic acid, higher levels of TCA/urea cycle intermediates, and 3-hydroxybutanoic acid correlated with better treatment outcomes in placebo group. Results of this study indicate that biochemical changes induced by drug continue to evolve over 4 weeks of treatment and that might explain partially delayed response. Response to drug and response to placebo share common pathways but some pathways are more affected by drug treatment. BCAAs seem to be implicated in mechanisms of recovery from a depressed state following sertraline treatment.

Pretreatment metabotype as a predictor of response to sertraline or placebo in depressed outpatients: a proof of concept.

The purpose of this study was to determine whether the baseline metabolic profile (that is, metabotype) of a patient with major depressive disorder (MDD) would define how an individual will respond to treatment. Outpatients with MDD were randomly assigned to sertraline (up to 150 mg per day) (N=43) or placebo (N=46) in a double-blind 4-week trial. Baseline serum samples were profiled using the liquid chromatography electrochemical array; the output was digitized to create a 'digital map' of the entire measurable response for a particular sample. Response was defined as ≥50% reduction baseline to week 4 in the 17-item Hamilton Rating Scale for Depression total score. Models were built using the one-out method for cross-validation. Multivariate analyses showed that metabolic profiles partially separated responders and non-responders to sertraline or to placebo. For the sertraline models, the overall correct classification rate was 81% whereas it was 72% for the placebo models. Several pathways were implicated in separation of responders and non-responders on sertraline and on placebo including phenylalanine, tryptophan, purine and tocopherol. Dihydroxyphenylacetic acid, tocopherols and serotonin were common metabolites in separating responders and non-responders to both drug and placebo. Pretreatment metabotypes may predict which depressed patients will respond to acute treatment (4 weeks) with sertraline or placebo. Some pathways were informative for both treatments whereas other pathways were unique in predicting response to either sertraline or placebo. Metabolomics may inform the biochemical basis for the early efficacy of sertraline.

Competitive inhibitors and allosteric activators of protein kinase C isoenzymes: a personal account and progress report on transferring academic discoveries to the clinic.

PKC (protein kinase C) isoenzymes are related protein kinases, involved in many signalling events in normal state and in disease. Basic research into identifying the molecular basis of PKC selectivity led to simple strategies to identify selective competitive inhibitor peptides and allosteric agonist peptides of individual PKC isoenzymes. The strategies and rationale used to identify these peptide regulators of protein-protein interaction may be applicable to other signalling events. Importantly, the PKC-regulating peptides proved to be useful pharmacological tools and may serve as drugs or drug leads for a variety of human diseases.

The roles of PKCdelta and epsilon isoenzymes in the regulation of myocardial ischaemia/reperfusion injury.

Reperfusion of ischaemic cardiac tissue is associated with increased apoptosis and oncosis, resulting in diminished heart function. Short bouts of ischaemia before the prolonged ischaemic event (ischaemic preconditioning) protect the heart from injury mediated by reperfusion. The PKC (protein kinase C) family of serine/threonine kinases are involved in many different signalling processes. Two calcium-insensitive isoforms of the novel PKC subfamily, PKCdelta and epsilon, play opposing roles in ischaemia/reperfusion injury. Activation of PKCdelta during reperfusion induces cell death through the regulation of mitochondrial function and induction of apoptosis and oncosis. In contrast, activation of PKCepsilon before ischaemia protects mitochondrial function and diminishes apoptosis and oncosis. How can two highly homologous PKC isoenzymes play such opposing roles through the regulation of mitochondrial function? This review will highlight what is known about PKCdelta and epsilon function during ischaemia/reperfusion injury and will suggest a novel regulatory pathway which determines the fate of the cell following ischaemic stress.

Quantitative surface EMG in the diagnosis of neuromuscular disorders.

This paper describes a non-invasive quantitative method for the diagnosis of neuromuscular disorders using surface EMG (sEMG). We found sEMG to be a reliable method that can be used to differentiate neuropathic and myopathic patients from the normal subjects. The multivariate discriminant analysis of sEMG data assisted in separating myopathic from neuropathic disorders. Nevertheless sEMG is not robust enough to replace needle EMG as a stand-alone diagnostic tool. However quantitative sEMG that is described in this paper could be adopted as a simple, rapid and non-invasive technique to be used in the out patients clinic by EMG-naive clinicians as a screening method for neuromuscular disorders, before referring the patients for detailed clinical neurophysiological examinations.

Polymorphism and evolution in the constant region of the T-cell receptor beta chain in an advanced teleost fish.

Sequence, PCR and Southern data are presented as evidence that, as in mammals, two gene loci encode C regions of the TCR beta chain in the bicolor damselfish, Stegastes partitus. The loci are distinguished by an insertion of ten amino acids in the c-d loop at one locus and by a high interlocus divergence of the third intron and fourth exon sequences. Unlike their mammalian counterparts, the damselfish TCRBC genes encode highly polymorphic regions. None of the eight complete cDNA or four partial genomic DNA sequences presented from a single animal are identical; and three of the four animals examined are heterozygous at both loci, suggesting high heterozygosity in the damselfish population. Coding regions of the eight cDNA clones differ by up to 12% at the DNA level and 23% at the amino acid level. Polymorphism is concentrated primarily in the less evolutionarily conserved regions, suggesting that this variation may be selectively neutral. However, a comparison of the variation between synonymous and non-synonymous sites suggests that at least a portion of the observed variation results from selection. As in mammals, a gradient of sequence homogenization between the two loci is observed. Data presented here suggest that both interlocus homogenization and the sharing of polymorphic segments are likely achieved by partial gene conversion.

Symptom-specific effects of fluoxetine in post-traumatic stress disorder.

The selective serotonin reuptake inhibitors have become a first line treatment for post-traumatic stress disorder (PTSD). In a recent double-blind study in civilians, fluoxetine produced clinically and statistically significant effects on all general measures of PTSD. We examined the specific effects of fluoxetine versus placebo in the above mentioned study of PTSD clusters and individual symptoms. Individuals were included if they met criteria for PTSD according to the Structured Clinical Interview for DSM-III-R (SCID). Symptoms were assessed at sequential time points by the Structured Interview for PTSD (SIP), a clinician interview based assessment, and a self-report scale, the Davidson Trauma Scale (DTS). A total of 53 patients were included in the analysis. On the SIP and DTS, fluoxetine was found to produce statistically significant changes on all clusters. Significant effects for fluoxetine were noted on 10 items of the DTS, and 8 items of the SIP. The SIP and DTS had 6 items in common that were significant. Fluoxetine exerts a broad spectrum effect in reducing all the symptom clusters of PTSD in this sample. The symptoms of being physically upset at reminders of the trauma, avoiding thoughts of the trauma, having difficulty enjoying things, feeling distant/estranged, having a sense of foreshortened future, and impaired concentration, were the symptoms most responsive to the effects of treatment with fluoxetine on both scales.

Nefazodone in post-traumatic stress disorder: results from six open-label trials.

Nefazodone, an antidepressant which blocks serotonin (5-HT)2 receptors and 5-HT reuptake, was evaluated in the treatment of post-traumatic stress disorder (PTSD) in six open-label studies involving both civilians and combat veterans. Our objective was to report this available pooled data to characterize the response of this drug in PTSD. Specifically, we looked at response rates using three different criteria, the effect of nefazodone on each PTSD cluster and individual symptoms and, lastly, variables that might predict response. One hundred and five outpatients with chronic PTSD were treated with nefazodone titrated up to 600 mg/day, 92 of whom were entered in an intent to treat analysis. We used the percentage drop in score between baseline and endpoint on main scale as a common measure to evaluate outcome. The response criterion of a drop in score of at least 30%, 40% and 50% revealed response rates of 46, 36 and 26%, respectively. Nefazodone showed a broad spectrum of action on PTSD symptoms. This profile might make nefazodone a useful drug to treat PTSD. Predictors of response include age, sex and trauma type. Double-blind, placebo-controlled clinical trials in PTSD are in progress to assess the utility of nefazodone as a treatment in this disorder.

Derivation of the SPAN, a brief diagnostic screening test for post-traumatic stress disorder.

The Davidson Trauma Scale (DTS) is a validated 17-item self-rating scale used in the diagnosis of post-traumatic stress disorder (PTSD), which is sensitive to the effects of treatment. It was felt that a shorter version of the scale might provide a better diagnostic screening tool. Subjects were drawn from a sample of 243 patients obtained from multiple cohorts that included a group of survivors of various forms of trauma, including natural disaster, rape and combat. All subjects had diagnostic assessments for PTSD with a clinical interview and completed the DTS. The data were randomly divided between two subsamples, and frequency and severity scores were calculated for the DTS. A four-item scale, the SPAN (named for its top four items: Startle, Physiological arousal, Anger, and Numbness), was developed. It demonstrated an efficiency of 0.88, sensitivity of 0.84, specificity of 0.91 and positive likelihood ratio of 9.1. In a replication sample, values were slightly lower but still acceptable (efficiency = 0.80). A subgroup of PTSD patients received either fluoxetine or placebo in a clinical trial, and a significant SPAN score improvement was observed on fluoxetine. The SPAN, which correlated significantly with the Impact of Events Scale, the Sheehan Disability Scale, and the Structured Interview of PTSD, was found to have a diagnostic accuracy of 88%.

Two tests of instance-based and abstract rule-based accounts of invariant learning.

Two manipulations are argued to distinguish between instance-based and abstract rule-based accounts of invariant learning. Three experiments examined the effects of manipulating the type of invariant feature in the learning set, and the type of training schedules prior to test. In line with traditional research, selection bias at test was present when the invariant was the consistent inclusion of a stimulus item in the learning set. However, the degree of bias was identical when the invariant was the consistent exclusion of the stimulus item. In addition, negative transfer of training was observed when subjects were trained on one learning set and then shifted training to the opposite learning set, but no positive transfer of training was observed when subjects were trained on one learning set and then continued training using the same learning set. These results are argued to be evidence for instance-based accounts of invariant learning.

Effect of continuous lateral rotational therapy on lung mucus transport in mechanically ventilated patients.

PURPOSE: Continuous lateral rotational therapy (CLRT) <40 degrees is a method of altering the position of the ventilated patient to help clear secretions from the lung. CLRT has not been shown to reduce the incidence of atelectasis or pneumonia but potentially offers a way to maximize positional drainage in these patients without producing adverse effects. Treatment intervention, bracketed by two (nonrotational) control periods. The purpose of this study was to determine if CLRT alters mucus transport in critically ill, intubated patients in the intensive care unit of a teaching hospital. MATERIALS AND METHODS: Thirteen critically ill, but stable, mechanically ventilated patients, mean age 74 years, were enrolled. They were placed supine on a Biodyne bed (KCI, San Antonio, Texas) and pressures in the cushions adjusted to patient's weight. A radiolabeled aerosol was delivered by bagging for 2 to 3 minutes and repeated measurements of lung radioactivity were obtained by imaging of the thorax over the following 3 hours. A 90-minute period of rotation of the bed, 30 degrees to either side was preceded and followed by two 45-minute control periods during which the patient remained supine and stationary on the bed. Coughs and suctions were recorded and blood gases obtained pre and post study. RESULTS: (1) The mucous clearance was slower than that reported in normal subjects and in ambulatory patients with COPD; (2) there was a slight, but not significant, increase in clearance during CLRT; (3) clearance reverted to pre-oscillation levels following therapy. Lack of significant effect may be attributed to too shallow an angle for rotation or too short an intervention period. CONCLUSION: Positional drainage effected by short duration CLRT did not appear to stimulate significant mucous removal from the lung in critically ill patients but also did not cause any adverse effects.

An investigation of cued recall of multiattribute stimuli.

Memory performance for sequences of letters positioned in particular spatial locations in a 3 x 3 grid was examined by requiring participants to recall attributes of the target stimuli given 1 or 2 features of the stimuli as cues. Cuing asymmetry was observed between the serial-position curves of object and sequential-order information, and location and sequential-order information, when the stimuli were presented in both the same and different locations. After correcting for response bias, this asymmetry was attenuated for the stimuli presented in different locations and was eliminated for the stimuli presented in the same location. Contrary to the predictions of the fragmentation hypothesis (G. V. Jones, 1976), asymmetry was also observed between object and location information. The roles of spatial location and response bias are offered as explanations for previous contradictory claims for cuing symmetry between item and order information.

Non-invasive quantitative EMG.

The EMG information obtained by surface recording is compared to needle derived data processed in an identical manner. Such quantitative analysis of EMG activity has been undertaken using needle electrodes and is a well recognised technique for clinical purposes (16). Results of a study comparing data collected simultaneously by surface and needle electrodes from normal healthy volunteers are presented as a preliminary to a similar study of neuropathic and myopathic patients. The EMG interference pattern during maximum voluntary contraction was analysed for turns and zero crossings as well as from frequency spectral data, and the results displayed on-line using an inexpensive novel transputer aided PC. It was found that quantitative studies of surface and needle data were directly comparable in one muscle such as tibialis anterior but very different in another, such as rectus femoris, where there were changes in signal characteristic at different depths. The variability between individuals appeared to be less marked when surface electrodes were used. Data from surface recordings also show a high degree of repeatability when collected over a period of time.