Monoamines and metabolites in autopsied brain tissue from cirrhotic patients with hepatic encephalopathy

Alterations in the metabolism of monoamine neurotransmitters have been proposed to be involved in the development of the hepatic encephalopathy (HE) associated with experimental and human liver failure. In order to evaluate this hypothesis, the monoamines and some of their metabolites were measured in homogenates of caudate nucleus (CAU), prefrontal (PFCo) and frontal cortex (FCo) dissected from brains obtained at autopsy from nine cirrhotic patients who had died in hepatic coma and an equal number of control subjects, free from neurological, psychiatric and hepatic disorders, matched for age and time interval from death to freezing of autopsied brain samples. Monoamine measurements were performed by high-performance liquid chromatography with ion-pairing and electrochemical detection after a simple extraction procedure. In all three regions investigated, concentrations of dopamine (DA) were unchanged in cirrhotic patients vs controls while its metabolites, 3-methoxytyramine (3-MT) and homovanillic acid (HVA) were selectively affected i.e.3-MT was found to be increased in CAU, while HVA levels were increased in FCo and CAU. DOPAC was also found to be unchanged in CAU. Noradrenaline (NA) levels were greatly increased in PFCo and FCo of cirrhotic patients but remained unchanged in CAU. No significant differences in the concentrations of either serotonin (5-HT) or of its precursor 5-hydroxytryptophan (5-HTP) were found in any of the three regions studied. However, 5-hydroxyindoleacetic acid (5-HIAA), the major metabolite of 5-HT, was increased in PFCo and CAU of cirrhotic patients. These findings show that selective alterations of catecholamine and 5-HT systems are involved in human HE and therefore, they may play an important role in the pathogenesis of certain neurological symptoms associated with this encephalopathy.     

Effects of sodium,lithium, and magnesium onIn vitro binding of [3H]SCH23390 in rat neostriatum and cerebral cortex

The effects of sodium, lithium, and magnesium on the in vitro binding properties of the D₁ antagonist [³H]SCH23390 were examined with membrane preparations from rat neostriatum (CPU; caudate-putamen) and cerebral cortex (CTX). The saturation binding isotherms for both tissues performed in the presence of 120 mM of either Na⁺ or Li⁺ revealed an increase in the affinity, as compared to that observed when the incubation buffer was composed of Tris-Cl 50 mM with MgCl₂ 1 mM alone. For the CPU there were no changes in the maximum binding capacity (B _max) in the different buffers used. In the case of the CTX, there was a loss of [³H]SCH23390 binding sites when either Na⁺ or Li⁺ 120 mM were added to the incubations, suggesting a lack of selectivity of this ligand in the absence of group IA cations. The agonist state of the [³H]SCH23390 binding site was studied in competition experiments with dopamine. The highest agonist affinity was obtained in 50 mM Tris-Cl buffer with 1 mM MgCl₂ while the addition of 120 mM of either Na⁺ or Li⁺ caused a 3- to 5-fold decrease in the potency of dopamine to compete with specific [³H]SCH23390 binding in both CPU and CTX. The presence of magnesium was essential for the competition experiments; i.e.: a concentration of 1 mM MgCl₂ was optimum to obtain dopamine antagonism of ligand binding, while increasing Mg²⁺ to 2 or 5 mM did not appear to further improve the inhibitions. The results support both agonist and antagonist affinity shifts for the dopamine D₁ receptor labeled with [³H]SCH23390. Receptor affinity studies should take into account that pharmacological specificity may vary with the incubation buffer utilized, especially when comparing binding data from different laboratories performed under varying ionic conditions.     

The self-incompatibility phenotype in brassica is altered by the transformation of a mutant S locus receptor kinase

The self-incompatible (SI) Brassica napus line W1, which carries the 910 S allele, was transformed with an inactive copy of the 910 S locus receptor kinase (SRK) gene. Two transformed lines were analyzed based on their heritable ability to set self-seed. The first line was virtually completely self-compatible (SC), and reciprocal pollinations with the original W1 line demonstrated that only the stigma side of the SI phenotype was altered. An analysis of the expression of endogenous SRK-910 demonstrated that the mechanism of transgene action is via gene suppression. Furthermore, the expression of the S locus glycoprotein gene present in the 910 allele (SLG-910), SLG-A10, which is derived from a nonfunctional S allele, and an S locus-related gene were also suppressed. When the transgene was crossed into another SI line carrying the A14 S allele, it was also capable of suppressing the expression of the endogenous genes and of making this line SC. The second transgenic line studied was only partly SC. In this case as well, only the stigma phenotype was affected, although no gene suppression was detected for endogenous SRK-910 or SLG-910. In this line, the expression of the transgene most likely was causing the change in phenotype, and no effect was observed when this transgene was crossed into the other SI line. Therefore, this work reinforces the hypothesis that the SRK gene is required, but only for the stigma side of the SI phenotype, and that a single transgene can alter the SI phenotype of more than one S allele.     

Effects of denervation and hyperinnervation on dopamine and serotonin systems in the rat neostriatum: implications for human Parkinson's disease

The research on central synaptic neurotransmission has greatly benefited from the use of the neurotoxin 2,4,5-trihydroxyphenylethylamine, or 6-hydroxydopamine (6-OHDA), that destroys catecholamine-containing neuronal cell bodies and nerve terminals. Refinements in the use of this neurotoxin led to the use of dopamine-denervated animals as models of human Parkinson's disease, in which the loss of dopaminergic neurons is a prominent feature. Here we review structural, pharmacological, and biochemical studies carried out in the adult and neonatal 6-OHDA lesioned animals. These models have become useful and interesting paradigms to examine alterations in the expression of receptors and in their sensitivity to agonist drugs; some of these modifications may underlie the altered responsiveness of the dopamine-lesioned animals to dopamine, but also to other compounds, including serotoninergic drugs. We have also reviewed studies of amino acids as well as of monoamine metabolism and of uptake mechanisms that may underlie some of the behavioural alterations in these models that have become relevant for our understanding of the sprouting and plastic properties of spared neurons, and of the alternate neuronal projections that replace lesioned terminals, enabling compensatory adaptations. Although 6-OHDA-lesioned animals, that display some biochemical characteristics of Parkinson's disease in humans, do not express all of the neurological features exhibited by patients, the increasing knowledge that can be obtained from studies in simplified experimental models will undoubtedly lead to the development of innovative drugs and other replacement therapies for degenerative brain diseases.     

Nico M. van Gelder,the Inquisitive Neurochemist

Neurochemical Research -     

Characterization of progenies ofTriticum aestivum-Psathyrostachys juncea derivatives by using genomicin-situ hybridization

Using genomicin-situ hybridization (GISH) technique, 7 translocation-addition lines, 6 translocation and translocation-addition lines, 2 ditelosomic addition lines and 1 translocation line were identified fromTriticum aestivum L. -Psathyrostachys juncea (Fisch.) Nevski intergeneric hybrids, of which translocation-addition and translocation and translocation-addition lines were not found in other reports. No substitutions and disornic additions were detected in the, hybrids and breakages occurred in allP. juncea chromosomes studied. Results have shown that the improved GISH technique is a rapid and economical method for use in this field.     

The cardiovascular effects of amodiaquine and structurally related antimalarials: An individual patient data meta-analysis

BackgroundAmodiaquine is a 4-aminoquinoline antimalarial similar to chloroquine that is used extensively for the treatment and prevention of malaria. Data on the cardiovascular effects of amodiaquine are scarce, although transient effects on cardiac electrophysiology (electrocardiographic QT interval prolongation and sinus bradycardia) have been observed. We conducted an individual patient data meta-analysis to characterise the cardiovascular effects of amodiaquine and thereby support development of risk minimisation measures to improve the safety of this important antimalarial.Methods and findingsStudies of amodiaquine for the treatment or prevention of malaria were identified from a systematic review. Heart rates and QT intervals with study-specific heart rate correction (QTcS) were compared within studies and individual patient data pooled for multivariable linear mixed effects regression.The meta-analysis included 2,681 patients from 4 randomised controlled trials evaluating artemisinin-based combination therapies (ACTs) containing amodiaquine (n = 725), lumefantrine (n = 499), piperaquine (n = 716), and pyronaridine (n = 566), as well as monotherapy with chloroquine (n = 175) for uncomplicated malaria. Amodiaquine prolonged QTcS (mean = 16.9 ms, 95% CI: 15.0 to 18.8) less than chloroquine (21.9 ms, 18.3 to 25.6, p = 0.0069) and piperaquine (19.2 ms, 15.8 to 20.5, p = 0.0495), but more than lumefantrine (5.6 ms, 2.9 to 8.2, p < 0.001) and pyronaridine (−1.2 ms, −3.6 to +1.3, p < 0.001). In individuals aged ≥12 years, amodiaquine reduced heart rate (mean reduction = 15.2 beats per minute [bpm], 95% CI: 13.4 to 17.0) more than piperaquine (10.5 bpm, 7.7 to 13.3, p = 0.0013), lumefantrine (9.3 bpm, 6.4 to 12.2, p < 0.001), pyronaridine (6.6 bpm, 4.0 to 9.3, p < 0.001), and chloroquine (5.9 bpm, 3.2 to 8.5, p < 0.001) and was associated with a higher risk of potentially symptomatic sinus bradycardia (≤50 bpm) than lumefantrine (risk difference: 14.8%, 95% CI: 5.4 to 24.3, p = 0.0021) and chloroquine (risk difference: 8.0%, 95% CI: 4.0 to 12.0, p < 0.001). The effect of amodiaquine on the heart rate of children aged <12 years compared with other antimalarials was not clinically significant. Study limitations include the unavailability of individual patient-level adverse event data for most included participants, but no serious complications were documented.ConclusionsWhile caution is advised in the use of amodiaquine in patients aged ≥12 years with concomitant use of heart rate–reducing medications, serious cardiac conduction disorders, or risk factors for torsade de pointes, there have been no serious cardiovascular events reported after amodiaquine in widespread use over 7 decades. Amodiaquine and structurally related antimalarials in the World Health Organization (WHO)-recommended dose regimens alone or in ACTs are safe for the treatment and prevention of malaria.

In this meta-analysis, Xin Hui Supanee Chan and colleagues investigate the cardiovascular effects of amodiaquine and structurally-related antimalarials using individual patient data from trials.     

Guiding farnesyltransferase inhibitors from an ECLiPS library to the catalytic zinc

Farnesyltransferase inhibitors identified from an ECLiPS library were optimized using solution-phase synthesis. X-ray crystallography of inhibited complexes was used to identify substructures that coordinate to the active site zinc. The X-ray structures were ultimately used to guide the design of second-generation analogs with FTase IC(50)s of less than 1.0 nM.     

An improved method using densitometry for evaluating severity of laser photocoagulation induced CNV

Laser photocoagulation induced choroidal neovascularization currently is the most effective model available for the study of this disease in terms of efficacy of new drugs and therapies. Previously, evaluating the extent of choroidal neovascularization using this model was time- consuming and required the use of experienced personnel. We describe a new method for simple and rapid evaluation of laser induced choroidal neovascularization using densitometry. Fluorescein angiograms of a laser photocoagulated rat eye were scanned into a computer. Densitometry software subsequently was used to calculate the severity of the laser lesions. The densitometry method proved effective for calculating the extent of laser induced choroidal neovascularization. In addition, this method was more rapid than visual evaluations and less likely to produce errors.