Transcriptional effects of carbon and nitrogen starvation on Ganoderma boninense, an oil palm phytopathogen

BACKGROUND

Ganoderma boninense is a phytopathogen of oil palm, causing basal and upper stem rot diseases.

METHODS

The genome sequence was used as a reference to study gene expression during growth in a starved carbon (C) and nitrogen (N) environment with minimal sugar and sawdust as initial energy sources. This study was conducted to mimic possible limitations of the C-N nutrient sources during the growth of G. boninense in oil palm plantations.

RESULTS

Genome sequencing of an isolate collected from a palm tree in West Malaysia generated an assembly of 67.12 Mb encoding 19,851 predicted genes. Transcriptomic analysis from a time course experiment during growth in this starvation media identified differentially expressed genes (DEGs) that were found to be associated with 29 metabolic pathways. During the active growth phase, 26 DEGs were related to four pathways, including secondary metabolite biosynthesis, carbohydrate metabolism, glycan metabolism and mycotoxin biosynthesis. G. boninense genes involved in the carbohydrate metabolism pathway that contribute to the degradation of plant cell walls were up-regulated. Interestingly, several genes associated with the mycotoxin biosynthesis pathway were identified as playing a possible role in pathogen-host interaction. In addition, metabolomics analysis revealed six metabolites, maltose, xylobiose, glucooligosaccharide, glycylproline, dimethylfumaric acid and arabitol that were up-regulated on Day2 of the time course experiment.

CONCLUSIONS

This study provides information on genes expressed by G. boninense in metabolic pathways that may play a role in the initial infection of the host.

Analysis of Coconut cadang-cadang viroid variants on field samples exhibiting variation in orange spotting symptom expression and severity

BACKGROUND

Sequence variation has been attributed to symptom variations but has not been investigated in Orange Spotting-Coconut cadang-cadang viroid (OS-CCCVd) infected palms. Likewise, the relationship between Coconut cadang-cadang viroid (CCCVd) variants, Orange Spotting (OS) severity and the accumulation of the viroid in the palms have not been elucidated. This paper describes the characterization of CCCVd variants by cloning and sequencing, followed by correlation with symptom expression.

METHODS AND RESULTS

Total nucleic acids were extracted from leaf samples harvested from frond 20 of seven Dura × Pisifera (D × P) African oil palm (Elaeis guineensis Jacq.) aged between 13 and 21 years old collected from local plantations. The nucleic acids were fractionated using 5% non-denaturing polyacrylamide gel electrophoresis (PAGE) before being subjected to detection by reverse transcribed polymerase chain reaction (RT-PCR). The PCR products were cloned into a plasmid vector and the sequence of the clones was analyzed. CCCVd variants were quantified using real-time qPCR assay with CCCVd specific primers. Sixteen randomly selected clones of (OP246) had an arbitrary 100% identity with CCCVdOP246 (GeneBank Accession No: HQ608513). Meanwhile, four clones had >93% similarity with several minor sequence variations forming variants of OP234, OP235, OP251 and OP279.

CONCLUSION

The OS symptoms observed in the field were characterized into three categories based on the size and morphology of the orange spots on the affected fronds. In addition, there was no direct correlation between disease severity and the accumulation of CCCVd variants in oil palm. This finding is the first report describing the sequence variation of the CCCVd RNA and symptom variation in OS oil palm field samples.

Synergism: biocontrol agents and biostimulants in reducing abiotic and biotic stresses in crop

In today's fast-shifting climate change scenario, crops are exposed to environmental pressures, abiotic and biotic stress. Hence, these will affect the production of agricultural products and give rise to a worldwide economic crisis. The increase in world population has exacerbated the situation with increasing food demand. The use of chemical agents is no longer recommended due to adverse effects towards the environment and health. Biocontrol agents (BCAs) and biostimulants, are feasible options for dealing with yield losses induced by plant stresses, which are becoming more intense due to climate change. BCAs and biostimulants have been recommended due to their dual action in reducing both stresses simultaneously. Although protection against biotic stresses falls outside the generally accepted definition of biostimulant, some microbial and non-microbial biostimulants possess the biocontrol function, which helps reduce biotic pressure on crops. The application of synergisms using BCAs and biostimulants to control crop stresses is rarely explored. Currently, a combined application using both agents offer a great alternative to increase the yield and growth of crops while managing stresses. This article provides an overview of crop stresses and plant stress responses, a general knowledge on synergism, mathematical modelling used for synergy evaluation and type of in vitro and in vivo synergy testing, as well as the application of synergism using BCAs and biostimulants in reducing crop stresses. This review will facilitate an understanding of the combined effect of both agents on improving crop yield and growth and reducing stress while also providing an eco-friendly alternative to agroecosystems.

Improved Growth Performance of Elaeis guineensis Jacq. Through the Applications of Arbuscular Mycorrhizal (AM) Fungi and Endophytic Bacteria

Agrochemical application in the oil palm industry has been estimated to be the largest component amounting to almost 30% of the operational costing. Therefore, there is a huge pressure in the oil palm cultivation to exercise sustainable practices, preferably using cheaper alternatives such as biofertilizers and organic substrates. This study investigates the effect of arbuscular mycorrhizal (AM) fungi and endophytic bacteria applied independently and in combination on oil palm growth and nutrient uptake. Greenhouse and field studies were conducted with plant responses assessed through growth parameters. Greenhouse plants were significantly stimulated by AM fungi, Rhizophagus intraradices UT126 (M1), through single microbe application. An increase of 36% in leaf area was noted in M1 plants while the calcium (Ca) uptake in leaves increased by 11%. There was no significant improvement in overall nitrogen, phosphate, and potassium (NPK) uptake but a significant improvement of Ca measurement in greenhouse and field was observed in the leaves. The predicted synergism between mixed inocula of M1 and R. clarus BR152B (M2) on vegetative growth was not observed, suggesting the probability of interspecies incompatibility that requires further investigation. Growth readings in plants treated with the combination of M1-M2 and Pseudomonas aeruginosa UPMP3 in the field were highest without a significant difference as compared to single application of M1. The difference in readings for field and greenhouse may have been influenced by other external factors such as soil type, rhizospheric microbial community, and climate, and therefore requires further elucidation. These findings suggest R. intraradices UT126 as a promising biostimulant candidate in sustainable agronomic practices especially in the nursery practices.

Timing of maternal immune activation and sex influence schizophrenia-relevant cognitive constructs and neuregulin and GABAergic pathways

Maternal immune activation (MIA) during pregnancy is an established environmental risk factor for schizophrenia. Timing of immune activation exposure as well as sex of the exposed offspring are critical factors in defining the effects of MIA. However, the specificity of MIA on the component structure of schizophrenia, especially cognition, has been difficult to assess due to a lack of translational validity of maze-like testing paradigms. We aimed to assess cognitive domains relevant to schizophrenia using highly translational touchscreen-based tasks in male and female mice exposed to the viral mimetic, poly(I:C) (5 mg/k, i.p.), during early (gestational day (GD) 9-11) and late (GD13-15) gestational time points. Gene expression of schizophrenia candidate pathways were assessed in fetal brain immediately following poly(I:C) exposure and in adulthood to identify its influence on neurodevelopmental processes. Sex and window specific alterations in cognitive performance were found with the early window of MIA exposure causing female-specific disruptions to working memory and reduced perseverative behaviour, while late MIA exposure caused male-specific changes to working memory and deficits in reversal learning. GABAergic specification marker, Nkx2.1 gene expression was reduced in fetal brains and reelin expression was reduced in adult hippocampus of both early and late poly(I:C) exposed mice. Neuregulin and EGF signalling were initially upregulated in the fetal brain, but were reduced in the adult hippocampus, with male mice exposed in the late window showing reduced Nrg3 expression. Serine racemase was reduced in both fetal and adult brain, but again, adult reductions were specific to male mice exposed at the late time point. Overall, we show that cognitive constructs relevant to schizophrenia are altered by in utero exposure to maternal immune activation, but are highly dependent on the timing of infection and the sex of the offspring. Glutamatergic and epidermal growth factor pathways were similarly altered by MIA in a timing and sex dependent manner, while MIA-induced GABAergic deficits were independent of timing or sex.

Bazedoxifene - a promising brain active SERM that crosses the blood brain barrier and enhances spatial memory

Over 20 years of accumulated evidence has shown that the major female sex hormone 17β-estradiol can enhance cognitive functioning. However, the utility of estradiol as a therapeutic cognitive enhancer is hindered by its unwanted peripheral effects (carcinogenic). Selective estrogen receptor modulators (SERMs) avoid the unwanted effects of estradiol by acting as estrogen receptor antagonists in some tissues such as breast and uterus, but as agonists in others such as bone, and are currently used for the treatment of osteoporosis. However, understanding of their actions in the brain are limited. The third generation SERM bazedoxifene has recently been FDA approved for clinical use with an improved biosafety profile. However, whether bazedoxifene can enter the brain and enhance cognition is unknown. Using mice, the current study aimed to explore if bazedoxifene can 1) cross the blood-brain barrier, 2) rescue ovariectomy-induced hippocampal-dependent spatial memory deficit, and 3) activate neural estrogen response element (ERE)-dependent gene transcription. Using liquid chromatography-mass spectrometry (LC-MS), we firstly demonstrate that a peripheral injection of bazedoxifene can enter the brain. Secondly, we show that an acute intraperitoneal injection of bazedoxifene can rescue ovariectomy-induced spatial memory deficits. And finally, using the ERE-luciferase reporter mouse, we show in vivo that bazedoxifene can activate the ERE in the brain. The evidence shown here suggest bazedoxifene could be a viable cognitive enhancer with promising clinical applicability.

Widespread white matter microstructural differences in schizophrenia across 4322 individuals: results from the ENIGMA Schizophrenia DTI Working Group

The regional distribution of white matter (WM) abnormalities in schizophrenia remains poorly understood, and reported disease effects on the brain vary widely between studies. In an effort to identify commonalities across studies, we perform what we believe is the first ever large-scale coordinated study of WM microstructural differences in schizophrenia. Our analysis consisted of 2359 healthy controls and 1963 schizophrenia patients from 29 independent international studies; we harmonized the processing and statistical analyses of diffusion tensor imaging (DTI) data across sites and meta-analyzed effects across studies. Significant reductions in fractional anisotropy (FA) in schizophrenia patients were widespread, and detected in 20 of 25 regions of interest within a WM skeleton representing all major WM fasciculi. Effect sizes varied by region, peaking at (d=0.42) for the entire WM skeleton, driven more by peripheral areas as opposed to the core WM where regions of interest were defined. The anterior corona radiata (d=0.40) and corpus callosum (d=0.39), specifically its body (d=0.39) and genu (d=0.37), showed greatest effects. Significant decreases, to lesser degrees, were observed in almost all regions analyzed. Larger effect sizes were observed for FA than diffusivity measures; significantly higher mean and radial diffusivity was observed for schizophrenia patients compared with controls. No significant effects of age at onset of schizophrenia or medication dosage were detected. As the largest coordinated analysis of WM differences in a psychiatric disorder to date, the present study provides a robust profile of widespread WM abnormalities in schizophrenia patients worldwide. Interactive three-dimensional visualization of the results is available at www.enigma-viewer.org.

Neuregulin-1 (NRG1) polymorphisms linked with psychosis transition are associated with enlarged lateral ventricles and white matter disruption in schizophrenia

BACKGROUND

Two single-nucleotide polymorphisms (SNPs) (rs4281084 and rs12155594) within the neuregulin-1 (NRG1) gene have been associated with psychosis transition. However, the neurobiological changes associated with these SNPs remain unclear. We aimed to determine what relationship these two SNPs have on lateral ventricular volume and white matter integrity, as abnormalities in these brain structures are some of the most consistent in schizophrenia.

METHODS

Structural (n = 370) and diffusion (n = 465) magnetic resonance imaging data were obtained from affected and unaffected individuals predominantly of European descent. The SNPs rs4281084, rs12155594, and their combined allelic load were examined for their effects on lateral ventricular volume, fractional anisotropy (FA) as well as axial (AD) and radial (RD) diffusivity. Additional exploratory analyses assessed NRG1 effects on gray matter volume, cortical thickness, and surface area throughout the brain.

RESULTS

Individuals with a schizophrenia age of onset ⩽25 and a combined allelic load ⩾3 NRG1 risk alleles had significantly larger right (up to 50%, p adj = 0.01) and left (up to 45%, p adj = 0.05) lateral ventricle volumes compared with those with allelic loads of less than three. Furthermore, carriers of three or more risk alleles, regardless of age of onset and case status, had significantly reduced FA and elevated RD but stable AD in the frontal cortex compared with those carrying fewer than three risk alleles.

CONCLUSIONS

Our findings build on a growing body of research supporting the functional importance of genetic variation within the NRG1 gene and complement previous findings implicating the rs4281084 and rs12155594 SNPs as markers for psychosis transition.

Sensory integration deficits support a dimensional view of psychosis and are not limited to schizophrenia

Visual dysfunction is commonplace in schizophrenia and occurs alongside cognitive, psychotic and affective symptoms of the disorder. Psychophysical evidence suggests that this dysfunction results from impairments in the integration of low-level neural signals into complex cortical representations, which may also be associated with symptom formation. Despite the symptoms of schizophrenia occurring in a range of disorders, the integration deficit has not been tested in broader patient populations. Moreover, it remains unclear whether such deficits generalize across other sensory modalities. The present study assessed patients with a range of psychotic and nonpsychotic disorders and healthy controls on visual contrast detection, visual motion integration, auditory tone detection and auditory tone integration. The sample comprised a total of 249 participants (schizophrenia spectrum disorder n=98; bipolar affective disorder n=35; major depression n=31; other psychiatric conditions n=31; and healthy controls n=54), of whom 178 completed one or more visual task and 71 completed auditory tasks. Compared with healthy controls and nonpsychotic patients, psychotic patients trans-diagnostically were impaired on both visual and auditory integration, but unimpaired in simple visual or auditory detection. Impairment in visual motion integration was correlated with the severity of positive symptoms, and could not be accounted for by a reduction in processing speed, inattention or medication effects. Our results demonstrate that impaired sensory integration is not specific to schizophrenia, as has previously been assumed. Instead, sensory deficits are closely related to the presence of positive symptoms independent of diagnosis. The finding that equivalent integrative sensory processing is impaired in audition is consistent with hypotheses that propose a generalized deficit of neural integration in psychotic disorders.

Meta-analysis reveals associations between genetic variation in the 5' and 3' regions of Neuregulin-1 and schizophrenia

Genetic, post-mortem and neuroimaging studies repeatedly implicate neuregulin-1 (NRG1) as a critical component in the pathophysiology of schizophrenia. Although a number of risk haplotypes along with several genetic polymorphisms in the 5' and 3' regions of NRG1 have been linked with schizophrenia, results have been mixed. To reconcile these conflicting findings, we conducted a meta-analysis examining 22 polymorphisms and two haplotypes in NRG1 among 16 720 cases, 20 449 controls and 2157 family trios. We found significant associations for three polymorphisms (rs62510682, rs35753505 and 478B14-848) at the 5'-end and two (rs2954041 and rs10503929) near the 3'-end of NRG1. Population stratification effects were found for the rs35753505 and 478B14-848(4) polymorphisms. There was evidence of heterogeneity for all significant markers and the findings were robust to publication bias. No significant haplotype associations were found. Our results suggest genetic variation at the 5' and 3' ends of NRG1 are associated with schizophrenia and provide renewed justification for further investigation of NRG1's role in the pathophysiology of schizophrenia.

An in vitro study of the antifungal activity of Trichoderma virens 7b and a profile of its non-polar antifungal components released against Ganoderma boninense

Ganoderma boninense is the causal agent of a devastating disease affecting oil palm in Southeast Asian countries. Basal stem rot (BSR) disease slowly rots the base of palms, which radically reduces productive lifespan of this lucrative crop. Previous reports have indicated the successful use of Trichoderma as biological control agent (BCA) against G. boninense and isolate T. virens 7b was selected based on its initial screening. This study attempts to decipher the mechanisms responsible for the inhibition of G. boninense by identifying and characterizing the chemical compounds as well as the physical mechanisms by T. virens 7b. Hexane extract of the isolate gave 62.60% ± 6.41 inhibition against G. boninense and observation under scanning electron microscope (SEM) detected severe mycelial deformation of the pathogen at the region of inhibition. Similar mycelia deformation of G. boninense was observed with a fungicide treatment, Benlate^® indicating comparable fungicidal effect by T. virens 7b. Fraction 4 and 5 of hexane active fractions through preparative thin layer chromatography (P-TLC) was identified giving the best inhibition of the pathogen. These fractions comprised of ketones, alcohols, aldehydes, lactones, sesquiterpenes, monoterpenes, sulphides, and free fatty acids profiled through gas chromatography mass spectrometry detector (GC/MSD). A novel antifungal compound discovery of phenylethyl alcohol (PEA) by T. virens 7b is reported through this study. T. virens 7b also proved to be an active siderophore producer through chrome azurol S (CAS) agar assay. The study demonstrated the possible mechanisms involved and responsible in the successful inhibition of G. boninense.

Application of arbuscular mycorrhizal fungi with Pseudomonas aeruginosa UPMP3 reduces the development of Ganoderma basal stem rot disease in oil palm seedlings

The effect of arbuscular mycorrhizal fungi (AMF) in combination with endophytic bacteria (EB) in reducing development of basal stem rot (BSR) disease in oil palm (Elaeis guineensis) was investigated. BSR caused by Ganoderma boninense leads to devastating economic loss and the oil palm industry is struggling to control the disease. The application of two AMF with two EB as biocontrol agents was assessed in the nursery and subsequently, repeated in the field using bait seedlings. Seedlings pre-inoculated with a combination of Glomus intraradices UT126, Glomus clarum BR152B and Pseudomonas aeruginosa UPMP3 significantly reduced disease development measured as the area under disease progression curve (AUDPC) and the epidemic rate (R L) of disease in the nursery. A 20-month field trial using similar treatments evaluated disease development in bait seedlings based on the rotting area/advancement assessed in cross-sections of the seedling base. Data show that application of Glomus intraradices UT126 singly reduced disease development of BSR, but that combination of the two AMF with P. aeruginosa UPMP3 significantly improved biocontrol efficacy in both nursery and fields reducing BSR disease to 57 and 80%, respectively. The successful use of bait seedlings in the natural environment to study BSR development represents a promising alternative to nursery trial testing in the field with shorter temporal assessment.

Decreased cortical muscarinic receptors define a subgroup of subjects with schizophrenia

Schizophrenia is widely acknowledged as being a syndrome, consisting of an undefined number of diseases probably with differing pathologies. Although studying a syndrome makes the identification of an underlying pathology more difficult; neuroimaging, neuropsychopharmacological and post-mortem brain studies all implicate muscarinic acetylcholine receptors (CHRM) in the pathology of the disorder. We have established that the CHRM1 is selectively decreased in the dorsolateral prefrontal cortex of subjects with schizophrenia. To expand this finding, we wanted to ascertain whether decreased cortical CHRMs might (1) define a subgroup of schizophrenia and/or (2) be related to CHRM1 genotype. We assessed cortical [(3)H]pirenzepine binding and sequenced the CHRM1 in 80 subjects with schizophrenia and 74 age sex-matched control subjects. Kernel density estimation showed that [(3)H]pirenzepine binding in BA9 divided the schizophrenia, but not control, cohort into two distinct populations. One of the schizophrenia cohorts, comprising 26% of all subjects with the disorder, had a 74% reduction in mean cortical [(3)H]pirenzepine binding compared to controls. We suggest that these individuals make up 'muscarinic receptor-deficit schizophrenia' (MRDS). The MRDS could not be separated from other subjects with schizophrenia by CHRM1 sequence, gender, age, suicide, duration of illness or any particular drug treatment. Being able to define a subgroup within schizophrenia using a central biological parameter is a pivotal step towards understanding the biochemistry underlying at least one form of the disorder and may represent a biomarker that can be used in neuroimaging.

Regional update: Cambodia

Cambodia is a developing south-east Asian country located in the fertile Mekong delta. Its recent past has been complicated by European colonialism and internal conflict. Health including mental health services are limited and sparse in regional and rural areas. Very constrained public mental health facilities and services are hampered by a shortage of a skilled workforce and insufficient training programs. The recent formation of the Mental Health Association of Cambodia promises to be a positive step forward in promoting mental health throughout the country.

Decreased muscarinic receptor binding in the frontal cortex of bipolar disorder and major depressive disorder subjects

BACKGROUND

Dysfunction of the cholinergic muscarinic receptors has been implicated in the pathology of bipolar disorder and major depressive disorder. However, there is conflicting evidence regarding the association between individual muscarinic receptors and the two disorders.

METHODS

We used the muscarinic receptor selective radioligands [3H]pirenzepine, [3H]AFDX-384 and [3H]4-DAMP to measure the levels of muscarinic(1) (CHRM1) and muscarinic(4) (CHRM4) receptors, muscarinic(2) (CHRM2) and muscarinic(4) (CHRM4) receptors and muscarinic(3) (CHRM3) receptor, respectively. Radioligand binding was measured in Brodmann's area (BA) 10 of the rostral prefrontal cortex, BA 46 of the dorsolateral prefrontal cortex and BA 40 of the parietal cortex in the post-mortem CNS from subjects with bipolar disorder or major depressive disorder and control subjects.

RESULTS

[3H]AFDX-384 binding was decreased in BA 46 in both bipolar disorder (p<0.01) and major depressive disorder (p<0.05). [3H]4-DAMP binding was decreased in BA 10 in bipolar disorder (p<0.05) but not major depressive disorder (p>0.05). [3H]AFDX-384 and [3H]4-DAMP binding were unaltered in any other cortical region examined for either disorder (p>0.05). [3H]pirenzepine binding was not significantly altered in either disorder in any cortical region examined (p>0.05).

LIMITATIONS

9 bipolar disorder, 9 major depressive disorder and 19 control subjects were used in the study.

CONCLUSION

Our data is consistent with previously published data implicating a role for CHRM2 receptors in the pathology of bipolar and major depressive disorder. The demonstration of a novel association between decreased CHRM3 receptor expression and bipolar disorder suggests bipolar and major depressive disorder differs in the underlying nature of their cholinergic dysfunction.

Acculturation is associated with the prevalence of tardive dyskinesia and akathisia in community-treated patients with schizophrenia

OBJECTIVE

Ethnicity is a risk factor for tardive dyskinesia (TD) and other antipsychotic drug-induced movement disorders (ADIMD). It is unclear whether this association is mediated through genetic, environmental or cultural factors individually or in combination. This pilot study aimed to explore this interaction by determining if acculturation in migrant groups contributed to the prevalence of ADIMD.

METHOD

Culturally diverse but relatively genetically homogeneous (white Caucasian) patients with schizophrenia (n = 40) treated at a single site were assessed for the presence of ADIMD and level of acculturation.

RESULTS

Higher levels of acculturation correlated with an increased prevalence of TD and akathisia but not Parkinsonism. The level of acculturation significantly predicted TD.

CONCLUSION

This study identifies for the first time that acculturation significantly contributes to the prevalence of TD and akathisia but not Parkinsonism in culturally diverse migrant populations and must be accounted for when explaining ethnic variation in rates of ADIMD.

Schizophrenia and bipolar affective disorder: perspectives for the development of therapeutics

Schizophrenia and bipolar disorder remain two of the most severe and difficult to treat psychotic disorders hampered by our poor understanding of their pathologies. The development of typical antipsychotic drugs opened an avenue of investigation through the dopamine D2 receptor in schizophrenia. With the reintroduction of the atypical antipsychotic clozapine came the development of a new generation of atypical agents and hypotheses challenging the centrality of this receptor in explaining antipsychotic effects. Evaluation of these competing theories does not provide sufficient evidence to displace the importance of the dopamine D2 receptor in antipsychotic efficacy, but does raise limitations of it as an explanatory hypothesis. Further, the treatment of other symptom domains in schizophrenia remains relatively neglected and open for the development of novel therapies. Similar to schizophrenia, bipolar disorder presents a diversity of clinical states but unlike schizophrenia, its mainstay of treatment, lithium, has not had a clear receptor target impeding understanding of the disorder's pathology and treatment. This has pushed investigation into other domains emphasising a number of intracellular signalling pathways and glial-neuronal interactions. The heavy genetic loading of bipolar disorder has allowed linkage analyses to identify a number of putative regions, however, the diversity of phenotypes complicates such studies. Polymorphisms of candidate genes have yielded potential leads such as dopamine beta hydroxylase in mood disorder and the serotonin transporter for treatment response. It is anticipated that combiningthe above approaches may hold promise for the development of more effective treatments.

Decreased hippocampal NMDA, but not kainate or AMPA receptors in bipolar disorder

OBJECTIVES

The purpose of this study was to determine whether there are changes in the density of ionotropic glutamate receptors in the hippocampus of subjects with bipolar disorder.

METHODS

Using in situ radioligand binding with semiquantitative autoradiography, we measured the density of [3H]MK-801, [3H]CGP39653, [3H]AMPA and [3H]kainate binding in hippocampi, obtained postmortem, from eight subjects with type 1 bipolar disorder and 8 age- and sex-matched controls.

RESULTS

In subjects with bipolar disorder there were significant decreases in the density of [3H]MK-801 binding in the Cornu Ammonis (CA) 3 (mean +/- SEM; 108.8 +/- 12.2 versus 166.2 +/- 18.0 fmol/mg ETE, p < 0.005) as well as the pyramidal (102.8 +/- 9.2 versus 136.6 +/- 11.2 fmol/mg ETE, p < 0.05) and polymorphic (21.73 +/- 6.5 versus 53.26 +/- 11.6 fmol/mg ETE, p < 0.05) layers of the subiculum. In addition, two-way analysis of variance (ANOVA) revealed a decrease in the density of [3H]CGP39653 binding across the hippocampal formation in bipolar subjects, which did not reach significance in any subregion. There were no changes in the densities of [3H]AMPA or [3H]kainate binding in these subjects.

CONCLUSIONS

[3H]CGP39653 and [3H]MK-801 bind to the glutamate binding site and open ion channel of the n-methyl-d-aspartate (NMDA) receptor, respectively. Therefore, these data suggest that there is a decrease in the number of open ion channels associated with no significant change in the apparent density of NMDA receptors in regions of the hippocampus from subjects with bipolar disorder.

Studies on [3H]CP-55940 binding in the human central nervous system: regional specific changes in density of cannabinoid-1 receptors associated with schizophrenia and cannabis use

A number of studies suggested that cannabis use can cause or exacerbate psychoses and may increase the risk of developing schizophrenia. These findings suggest that changes in the cannabinoid system of the brain may be involved in the pathology of schizophrenia. To determine whether changes in the cannabinoid system were present in the brains of subjects with schizophrenia, we used in situ radioligand binding and autoradiography to measure the binding of [3H]CP-55940 to the cannabinoid-1 receptor in the dorsolateral prefrontal cortex (Brodmann's area 9), caudate-putamen and areas of the temporal lobe from schizophrenic and control subjects, some of whom had ingested cannabis close to death. There was an increase in the density of [3H]CP-55940 binding to cannabinoid-1 receptors in the dorsolateral prefrontal cortex from subjects with schizophrenia (mean+/-S.E.M.: 142+/-9.9 vs 119+/-6.6fmol/mg estimated tissue equivalents; P<0.05) that was independent of recent cannabis ingestion. There was an increase in the density of cannabinoid-1 receptors in the caudate-putamen from subjects who had recently ingested cannabis (151+/-9.0 vs 123+/-7.2fmol/mg estimated tissue equivalents; P<0.05) that was independent of diagnoses. These data indicate that there are changes in cannabinoid-1 receptors in the dorsolateral prefrontal cortex that may prove to be associated with the pathology of schizophrenia. By contrast, changes in the density of cannabinoid-1 receptors may occur in the caudate-putamen in response to cannabis ingestion.

Typical and atypical neuroleptic drugs decrease platelet 3H-dopamine uptake in the rat

Reports of opposing changes in platelet 3H-dopamine uptake in neuroleptic-free versus neuroleptic-treated schizophrenic subjects have suggested an effect of neuroleptic treatment on this measure. We examined platelet 3H-dopamine uptake in rats treated with haloperidol or clozapine to determine if such treatment did affect platelet 3H-dopamine uptake. Neuroleptic drug treatment reduced platelet 3H-dopamine uptake in a dose- and time-dependent manner. After up to 4 weeks of treatment, these effects were reversed by the discontinuation of neuroleptic drug treatment. These data suggest that the effect of neuroleptic treatment in studies of platelet 3H-dopamine uptake could account for the variable findings in schizophrenia.

Platelet [3H]dopamine uptake is differentially affected by neuroleptic drug treatment in schizophrenia and schizophreniform disorder

1. The uptake of [3H] dopamine was measured using platelet-rich plasma (PRP) from neuroleptic-free subjects and again, in some cases, after the subject had been treated with neuroleptic drugs. 2. There were no differences in [3H]dopamine uptake by PRP in subjects who were or were not mentally ill. 3. After treatment with neuroleptic drugs the Km for platelet [3H] dopamine uptake had increased in 76% of subjects with schizophrenia and 87% of subjects with schizophreniform disorder. Similarly, the Vmax for platelet [3H]dopamine uptake had increased in 81% of the subjects with schizophrenia and 86% of the subjects with schizophreniform disorder. 4. By contrast, the Km for platelet [3H]dopamine uptake had decreased in 94% of subjects who had a psychoses associated with an illness other than schizophrenia or schizophreniform-disorder whilst the Vmax for platelet [3H]dopamine uptake also decreased by 94% in these subjects. 5. In subjects with psychoses, platelet [(3)H] dopamine uptake is differentially altered during neuroleptic drug treatment depending on diagnosis.

The development of a method to measure [3H] dopamine uptake by washed platelets provides no evidence for circulating inhibitors of platelet dopamine uptake in schizophrenia

Altered [3H] dopamine uptake by platelet-rich plasma (PRP) has been reported in some subjects with schizophrenia (Rotman et al 1980; Dean et al 1990). As platelet dopamine uptake was measured using PRP, it was not possible to determine if the changes in schizophrenia were intrinsic to the platelet or due to plasma factors. Furthermore, the constraints of plasma as a medium for platelet suspension has hindered the study of the physiological requirements of platelet dopamine uptake. A method is now reported that allows platelets to be suspended in a controlled medium while preserving the dopamine uptake mechanism of the platelet. Dopamine uptake by platelets in a controlled medium was dependent on temperature, energy, sodium, and chloride. Furthermore, plasma from subjects with schizophrenia and schizophreniform disorder did not significantly alter [3H] dopamine uptake by platelets compared to the effect of plasma from control subjects. Hence, these data provide no evidence for a circulating inhibitor of platelet [3H] dopamine uptake in plasma from subjects with schizophrenia.

Identification of a dopamine-binding protein on the membrane of the human platelet

The binding of [3H]dopamine to platelet membranes has been examined in an attempt to identify the putative dopamine-uptake mechanism of the platelet. [3H]Dopamine has been shown to bind to a 42,000 Da glycoprotein in platelet membrane with high affinity (Kd = 22.6 nM) and binding of [3H]dopamine was competed for by dopamine, molecules with catechol moieties, 5-hydroxytryptamine, GSH and ascorbic acid. Differences in pharmacological profile and molecular mass suggest that [3H]dopamine does not bind to a known receptor, a neuronal-type dopamine transporter or the platelet 5-hydroxytryptamine-uptake site. It is proposed that this novel binding site for dopamine, which has been purified 1000-fold from particulate platelet membrane, is likely to be a component of the dopamine-uptake mechanism of the human platelet.