Directly coupled high-performance liquid chromatography and nuclear magnetic resonance spectroscopic with chemometric studies on metabolic variation in Sprague--Dawley rats

We report here the first combined use of NMR-PR (pattern recognition) analysis and directly coupled HPLC--NMR analysis to identify metabolic subpopulations in normal laboratory animals and their discriminating endogenous urinary biomarkers. Urine samples obtained from control Sprague-Dawley rats (n = 68) were analyzed using (1)H NMR spectroscopy and principal components (PC) analysis to investigate physiological variability. Two distinct subpopulations of animals were classified based on metabolite excretion profiles. Analysis of the PC loadings established the spectral regions that were responsible for classification of the subpopulations and was used to direct the identification of biomarkers using a directly coupled HPLC--NMR analysis. One population had low urinary hippurate levels together with an increased concentration of 3-(3-hydroxyphenyl)propionic acid (3-HPPA)and 3-hydroxycinnamic acid (3-HCA). The other subpopulation excreted high levels of hippurate. Thus, we report the bimodal occurrence of hippuric acid and chlorogenic acid metabolites in a genetically homogeneous population of rats maintained under identical conditions, which may have significance in relation to the understanding of the consequences of biochemical variation in animals used for drug toxicity testing.     

Herpes simplex virus type 1 promoter activity during latency establishment, maintenance, and reactivation in primary dorsal root neurons in vitro

A neonatal rat dorsal root ganglion-derived neuronal culture system has been utilized to study herpes simplex virus (HSV) latency establishment, maintenance, and reactivation. We present our initial characterization of viral gene expression in neurons following infection with replication-defective HSV recombinants carrying beta-galactosidase and/or green fluorescent protein reporter genes under the control of lytic cycle- or latency-associated promoters. In this system lytic virus reporter promoter activity was detected in up to 58% of neurons 24 h after infection. Lytic cycle reporter promoters were shut down over time, and long-term survival of neurons harboring latent virus genomes was demonstrated. Latency-associated promoter-driven reporter gene expression was detected in neurons from early times postinfection and was stably maintained in up to 83% of neurons for at least 3 weeks. In latently infected cultures, silent lytic cycle promoters could be activated in up to 53% of neurons by nerve growth factor withdrawal or through inhibition of histone deacetylases by trichostatin A. We conclude that the use of recombinant viruses containing reporter genes, under the regulation of lytic and latency promoter control in neuronal cultures in which latency can be established and reactivation can be induced, is a potentially powerful system in which to study the molecular events that occur during HSV infection of neurons.     

Prior exposure to methylenedioxyamphetamine (MDA) induces serotonergic loss and changes in spontaneous exploratory and amphetamine-induced behaviors in rats

The substituted amphetamine 3,4 methylenedioxyamphetamine (MDA) is a popular recreational drug of abuse. Administration of MDA to experimental animals has been shown to induce damage to serotonergic axons and nerve terminals. However, there is a lack of information on whether these treatments can produce any long-term changes in behavioural performance particularly under stressful conditions. In the present study, MDA (7.5 mg/kg; i.p.) was administered twice daily to adult male Sprague Dawley rats for four days. Four weeks following the last dose, spontaneous behaviors of these animals were tracked and scored in a novel "open field" environment using an automated video registration and computer interpretation system. Changes in behavior were observed in MDA treated animals including reductions in exploratory oriented behaviors (locomotion and rearing) and increases in grooming behavior when compared to vehicle treated controls. MDA-treated animals also displayed an enhanced locomotor and stereotyped response to d-amphetamine (12 mg/kg; i.p.). Significant reductions in 5-HT concentrations (20-30%) were observed in the frontal cortex, amygdala, striatum, and hypothalamus as a result of MDA treatment. In addition, [3H] paroxetine binding was reduced by (40%) in the cortex of MDA treated rats indicating that the decrease in 5-HT concentrations were accompanied by a reduction in intact presynaptic 5-HT nerve terminals. Changes in behavioural performance in a novel "open field" environment and following d-amphetamine challenge might be considered as a behavioural model of serotonergic deficit induced by MDA. The findings of this study also suggest that MDA use may increase both the abuse potential, and the propensity to develop psychosis as a result of abusing other psychostimulants such as d-amphetamine.     

Calcium signals in long-term potentiation and long-term depression

We describe postsynaptic Ca2+ signals that subserve induction of two forms of neuronal plasticity, long-term potentiation (LTP) and long-term depression (LTD), in rat hippocampal neurons. The common induction protocol for LTP, a 1-s, 50-Hz tetanus, generates Ca2+ increases of about 50-Hz in dendritic spines of CA1 neurons. These very large increases, measured using a low affinity indicator (Mg fura 5), were found only in the spines and tertiary dendrites, and were dependent upon influx through N-methyl-D-aspartate (NMDA) gated channels. High affinity Ca2+ indicators (e.g., fura 2) are unable to demonstrate these events. In acute slices, neighboring dendritic branches often showed very different responses to a tetanus, and in some instances, neighboring spines on the same dendrite responded differently. LTD in mature CA1 neurons was induced by a low frequency stimulus protocol (2 Hz, 900 pulses), in the presence of GABA- and NMDA-receptor blockers. This LTD protocol produced dendritic Ca2+ increases of <1 microM. Duration of the Ca2+ increase was approximately 30 s and was due to voltage-gated Ca2+ influx. Finally, the ability of synaptically addressed Ca2+ stores to release Ca2+ was studied in CA3 neurons and was found to require immediate preloading and high intensity presynaptic stimulation, conditions unlike normal LTP-LTD protocols.     

Differential effect of chronic antidepressant treatments on lipopolysaccharide-induced depressive-like behavioural symptoms in the rat

In the present study we observed that lipopolysaccharide (LPS) administration provoked a characteristic reduction in body weight gain, food consumption, saccharin (but not water) consumption and nocturnal locomotor activity. It has been previously suggested that the ability of LPS to suppress the consumption of, and preference for, a palatable solution such as saccharin without altering water consumption, may represent an anhedonic response. The results of the present study demonstrate that chronic treatment with the tricyclic antidepressant (TCA) desipramine (7.5 mg/kg; i.p.) prevented LPS-induced anorexia, loss of body weight, the antidipsogenic effect and hypoactivity. In contrast, chronic treatment with the antidepressants paroxetine (7.5 mg/kg; i.p.) and venlafaxine (10 mg/kg; i.p.) failed to alter any of the LPS-induced behavioural responses. Furthermore, chronic treatment with desipramine (and to a lesser extent paroxetine) reduced the consumption of, and preference for, saccharin suggesting that these antidepressant treatments induce an "anhedonic" response in their own right. In conclusion, chronic desipramine treatment attenuated LPS-induced depressive-like behavioural symptoms in the rat. However, chronic treatment with paroxetine and venlafaxine did not significantly alter LPS-induced behavioural responses. The results of the present study support the hypothesis that TCA's may exert part of their anti-depressive efficacy through their effects on the immune system. However, this property does not appear to be shared by newer antidepressants which possess a better side effect profile than the TCA's. The suppressive effect of TCA's on proinflammatory cytokine secretion is discussed as a mechanism by which these agents alter LPS-induced behavioural responses.     

An expanded comparative map of bovine chromosome 27 targeting dairy form QTL regions

At present, the density of genes on the bovine maps is extremely limited and current resolution of the human-bovine comparative map is insufficient for selection of candidate genes controlling many economic traits of interest in dairy cattle. This study describes the chromosomal mapping of 10 selected gene-associated markers to bovine linkage and radiation hybrid maps to improve the breakpoint resolution in the human-bovine comparative map near two previously identified quantitative trait loci for the linear type trait, dairy form. Two regions of conserved synteny not previously described are reported between the telomeric region of bovine chromosome 27 (BTA27) and human chromosome 3 (HSA3) p24 region and between the HSA4q34.1 region and BTA8. These data increase the number of genes positioned on the bovine gene maps, refine the human-bovine comparative map, and should improve the efficiency of candidate gene selection for the dairy form trait in cattle.     

What can we learn from noncoding regions of similarity between genomes?

Background  

In addition to known protein-coding genes, large amounts of apparently non-coding sequence are conserved between the human and mouse genomes. It seems reasonable to assume that these conserved regions are more likely to contain functional elements than less-conserved portions of the genome.     

Visual attention: bottom-up versus top-down

Visual attention is attracted by salient stimuli that 'pop out' from their surroundings. Attention can also be voluntarily directed to objects of current importance to the observer. What happens in the brain when these two processes interact?