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R M Marchbanks

Publications and source records attributed to R M Marchbanks.

At least 19 recordsLinked to original sources
PubMed2003

A mitochondrial DNA sequence variant associated with schizophrenia and oxidative stress.

We have previously reported a changed mitochondrial (mt) gene expression in brain from patients with schizophrenia [Schizophr. Res. 14 (1995) 203]; now, we describe the distribution in the mtDNA from lymphocytes of a heteroplasmic sequence variation that was originally found in the mtDNA from the postmortem brain of a patient with schizophrenia. The variant is m.12027T>C and results in the change from isoleucine to threonine at position 423 of the ND4 subunit of NADH-ubiquinone reductase. Using a PCR-RFLP method, we have determined the heteroplasmy as the ratio of variant to total (variant ratio) at m.12027 in 184 controls and 181 patients with schizophrenia as well as 24 postmortem brain samples. The distribution of variants is bimodal having peaks at variant ratios of 0.262 and 0.732. The variant-rich fraction is very significantly associated with schizophrenia in males (47%), while there is only 18% in control males. There are significantly more variant-rich control females (36%) than control males (18%), suggesting that the female population is less sensitive to the presence of a variant in terms of liability to schizophrenia. In variant-rich samples from postmortem brain originating from both sexes, there is an increased superoxide production, suggesting that the variation contributes to oxidative stress. Antioxidant glycosides, such as quercetin rutoside, quench the superoxide production without (in contrast to neuroleptic drugs) interfering with the electron transfer activity of the reductase.

Adult↗
PubMed1998

Superoxide, neuroleptics and the ubiquinone and cytochrome b5 reductases in brain and lymphocytes from normals and schizophrenic patients.

The effects of the neuroleptic flupenthixol on the expression of the genes coding for the mitochondrial ubiquinone and cytochrome b5 reductases have been studied because of the importance of these enzymes in energy metabolism, oxidative stress and also because similar but oppositely directed changes have been previously observed in the cerebral cortex from schizophrenics. The neuroleptic flupenthixol reduces the expression in rats of the gene coding for NADH-cytochrome b5 reductase as measured by in situ hybridisation and its enzymic manifestation. Flupenthixol also reduces the enzymic activity of the mitochondrial NADH-ubiquinone reductase, and it has been previously shown that mRNA from the mitochondrially coded parts of the enzyme are reduced by the drug. Both the cis- and therapeutically less active trans-flupenthixol were found to produce these changes in rats. Post-mortem brain tissue from schizophrenics who have received neuroleptic medication have reduced levels of both reductases as measured enzymically, Lymphocyte samples from schizophrenics also have reduced levels of both reductases compared with normals. The superoxide anion O2- is the principle agent of oxidative stress and both the cytochrome b5 and the ubiquinone reductase enzymes were semi-purified from sheep liver and shown to produce appreciable amounts of superoxide. Superoxide production is reduced in brain homogenates from rats treated with flupenthixol. Its production is also reduced in brain tissue and lymphocytes from schizophrenics receiving neuroleptic medication. We conclude that neuroleptic medication reduces the expression of both the ubiquinone and cytochrome b5 reductase and among the effects of this reduction is a decrease in the production of neurotoxic superoxide.

Adult↗
PubMed1996

Mitochondrial involvement in schizophrenia and other functional psychoses.

Gene expression has been studied in post-mortem frontal cortex samples from patients who had suffered from schizophrenia and depressive illness. mRNA was extracted and characterised by translation and separation of the products by 2D gel electrophoresis. Post-mortem artefacts and the agonal experience did not affect the size distribution or amount of specific translation products. Four expression products were specifically reduced in samples from schizophrenics compared with normals. The expression of six products was altered in affective disorder, one in common with schizophrenia, two the same as in schizophrenia but increased. cDNA libraries were produced from the mRNA samples and 5 clones present at abnormal levels in schizophrenia identified by differential screening, isolated and sequenced. All the sequences encode mitochondrial transcripts; four encode mitochondrial rRNA and one the amino acid sequence of cytochrome oxidase sub-unit II. Increased cytochrome oxidase transcripts were found in a further set of mRNA extracts from schizophrenic patients including two who had not received neuroleptic medication. The effects of neuroleptic administration as exemplified by alpha-flupenthixol compared with the ineffective beta-flupenthixol were studied in experimental animals. It was found that 13 out of 28 clones whose levels were altered were mitochondrial in origin including rRNA, COX I & II and the NADH-Q reductase. Those encoding respiratory enzymes were at abnormally low levels as a result of alpha-flupenthixol administration. Measurements of the enzymic activity of cytochrome c oxidase in post-mortem frontal cortex of schizophrenics did not indicate any differences in overall activity but there was a decreased sensitivity to azide that was abolished by neuroleptics. Studies on NADH-cytochrome c reductase showed that schizophrenics whether medicated or not had a reduced rotenone sensitive activity that was compensated for by increased rotenone insensitive activity. We conclude that changes in mitochondrial gene expression are involved in schizophrenia and probably other functional psychoses.

Adult↗
PubMed1995

Astrocyte transplants alleviate lesion induced memory deficits independently of cholinergic recovery.

Basal forebrain tissue fragments taken from embryonic day 15 were separated into primary astrocytes and primary neurons in culture and grafted to rats with alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid lesions to the nucleus basalis and medial septal regions. The two cell types were compared in two experimental paradigms for their behavioural, biochemical and histochemical effects; standard transplants of whole basal forebrain and sham transplants served as positive and negative controls, respectively. Each transplant cell type was characterised by in vitro immunocytochemistry to assess content and purity. Memory deficits produced by the lesions in a spatial win-stay T-maze task (Experiment 1) and a spatial plus associative radial maze task (Experiment 2) were significantly improved by the astrocyte, but not by the neuronal, primary cell transplants. The astrocyte graft groups performed as well as standard cholinergic rich basal forebrain groups, reaching control levels on both tasks, while the neuronal transplant groups were not significantly different to lesioned (sham transplanted) rats. There was no recovery in choline acetyltransferase activity in brain regions containing astrocyte grafts whereas activity in the neuronal graft regions was increased (often to control levels), similar to recovery produced by basal forebrain grafts. Grafts in all groups survived, transplanted neurons displaying similar morphology and placement in the host brain to unseparated basal forebrain grafts, while astrocytes showed evidence of migration. The cultured astrocytes were estimated to be > 95% pure, showing positive staining for all astrocyte markers and an absence of staining for neuronal markers. The results indicate that the restoration of cognitive function following fetal grafting is not dependent upon a restoration of cholinergic neuronal activity but is more likely mediated via diffuse graft-host communication, with trophic secretion a probable factor. This study emphasizes the usefulness of astrocytes in the repair of central nervous system injury and has implications for therapeutic potential.

Animals↗
PubMed1995

A study of altered gene expression in frontal cortex from schizophrenic patients using differential screening.

In order to examine the molecular basis of schizophrenia we have employed a sequential differential hybridisation protocol to isolate mRNAs whose abundances are altered in schizophrenic compared to normal frontal cortex. Five cDNAs present at abnormal levels in the schizophrenic brain have been isolated by this method. The sequences were identified on the basis of homologies in the EMBL and Genbank databases. All the sequences encode mitochondrial transcripts; one encodes part of the 12s rRNA, three encode parts of the 16s rRNA region of the mitochondrial genome whilst the fourth encodes part of the amino acid sequence of cytochrome oxidase sub-unit II. It was established that mitochondrial sequences were not over-represented in the library and that this could therefore not account for the isolation of five mitochondrial transcripts by this procedure. Increased levels of cytochrome oxidase mRNA were detected in a further set of extracts from the frontal cortex of eight schizophrenic patients and five controls. The amount of mt-DNA was measured in these samples but there was no difference between schizophrenic and control. These results indicate a possible abnormality of mitochondrial function in the schizophrenic frontal cortex.

Adult↗
PubMed1994

Immunoidentification of cellular brain proteins associated with cognitive recovery in brain transplants.

In adult, lesion-impaired rat brain receiving embryonic day 15 (E15) fetal transplants, the level of expression of glial fibrillary acidic protein (GFAP) correlates positively with choline acetyltransferase (ChAT) levels and also with measurements of successful behavioural recovery. These results suggest that glial cells may play a pivotal role in the cognitive success of so-called cholinergic-rich transplants. The objective of this study was to investigate the association between GFAP- and ChAT-staining antigens in or around cholinergic-rich fetal grafts transplanted in adult cortex. An immunohistochemical fluorescent double-labelling technique was used to simultaneously identify GFAP- and ChAT-staining cells to assess whether there was a different type or distribution of cells present in these successful transplants. On brain sections of transplant area, GFAP-staining glial cells did not co-label with ChAT-staining cells. The transplant area, therefore, did not reveal a different type of cell from those seen in comparable normal cortical brain but rather a greater concentration of both GFAP- and ChAT-positive staining cells.

Animals↗
PubMed1993

Heterosynaptic short-term depression of population spike amplitude in the pyramidal layer of the CA1 hippocampal region evoked by a theta-like tetanization.

Heterosynaptic short-term depression (STD) of the stratum radiatum and stratum oriens inputs to the CA1 region was studied in rat hippocampal slices. STD was evoked by trains of 1050 impulses with interstimulus interval (ISI) variable from 10 to 700 ms. The STD was found to be very pronounced for tetanizations with ISI around 200 ms, and almost absent for ISI less than 50 ms or more than 500 ms. These data show that theta-like tetanization is an effective pattern not only for induction of the long-term potentiation (LTP), as has been shown previously, but for production of the heterosynaptic STD as well. This implies that heterosynaptic STD can effectively modulate induction of LTP by theta-like tetanization, and plays an important role in differentiation of potentiated pathways. It is discussed that the theta-like tetanization-induced release of ACh is a possible mechanism of the STD.

Afferent Pathways↗
PubMed1993

Behavioral parameters of the spatial memory correlate with the potentiation of the population spike, but not with the population excitatory postsynaptic potential, of the CA1 region in rat hippocampal slices.

Rats were tested for spatial performance in a water maze with further in vitro investigation of short-term and long-term potentiation (STP and LTP) in the CA1 region of the hippocampus. Recordings of the population spike in stratum pyramidale and population excitatory postsynaptic potential (EPSP) in stratum radiatum were made with extracellular electrodes after stimulation of the radiatum and oriens inputs in the region. It was found that for both inputs, STP and LTP of the population spike amplitude correlated with behavioral parameters of memory: latency of reaching the hidden platform (escape latency) and percent of time which the animal spent inside the quadrant with the platform. Potentiation of the initial slope of EPSP, in contrast, did not correlate with these parameters. These data support the hypothesis that hippocampal LTP may underlie spatial performance and show that potentiation of the output characteristic of the hippocampus (population spike), but not of the EPSP, is a physiological correlate for spatial memory.

Action Potentials↗
PubMed1992

Changes in relative levels of specific brain mRNA species associated with schizophrenia and depression.

Total cellular polyadenylated RNA (poly(A)+ RNA, mRNA) was prepared after guanidinium thiocyanate extraction of frozen brain tissue from age-matched controls and patients suffering from schizophrenia and unipolar depression. These mRNA populations were analysed by in vitro translation followed by two-dimensional gel analysis. Data were obtained from fluorograms derived from 10 different schizophrenic patients, 10 different controls and 5 different depressive patients. The relative concentrations of mRNA species coding for 4 translation products (33 kDa, pI 5.8; 26 kDa, pI 5.8; 35 kDa, pI 7.1; 23 kDa, pI 6.1) were significantly reduced in schizophrenia compared to controls when determined by computerised image analysis of the fluorograms. In the case of depression, the relative concentrations of mRNA species coding for 6 translation products were significantly altered, 4 being increased (38 kDa, pI 6.2, 17 kDa, pI 5.7, 35 kDa, pI 7.1; 23 kDa, pI 6.1) and two decreased (34 kDa, pI 6.2; 33 kDa, pI 5.8). Three translation products were altered in both schizophrenia and depression, one (33 kDa, pI 5.8) being altered according to the same trend, a decrease relative to controls, but two (35 kDa, pI 7.1; 23 kDa, pI 6.1) being altered differently in schizophrenia (reduced) and depression (increased). The effects of post mortem delay, mode of death and drug treatment on mRNA composition were also examined and found not to affect the levels of these translation products significantly. The significance of these changes will be discussed in relation to their relevance of biological mechanisms in the psychoses.

Aged↗
PubMed1992

Changes in brain gene expression in schizophrenic and depressed patients.

Poly(A+) mRNA was extracted from the post-mortem brain of schizophrenics (9 subjects), unipolar depressives (5 subjects) and controls (10 subjects) and used to direct the in vitro translation of radiolabelled protein in a cell-free reticulocyte-lysate system. Protein species were analysed on two-dimensional gels. Over 200 products were detected and, from these, 74 well-resolved species were chosen for further analysis. The optical density of each product was quantified by image analysis and normalised with respect to overall gel intensity. It was found that 7 novel, uncharacterised protein species, ranging from molecular weights (Mr) 17 kDa to 38 kDa and apparent isoelectric points (pI) 5.7-7.1, changed significantly in intensity in the psychotic groups compared to controls. One species changed only in the schizophrenia group (Mr = 26 kDa, pI = 5.8, 18% of control intensity) and 3 changed only in the depressive group (Mr = 38 kDa, pI = 6.2, 540% of control; Mr = 34 kDa, pI = 6.2, 6% of control; Mr = 17 kDa, pI = 5.7, 238% of control). Three further protein species were common to both psychotic groups (one species decreased in both schizophrenia and depression, Mr = 33 kDa, pI = 5.8; two species showed opposing intensity changes, decreasing in schizophrenia and increasing in depression, Mr = 35 kDa, pI = 7.1; Mr = 23 kDa, pI = 6.1). None of these changes was a function of post-mortem delay or mode of death. It is quite likely that such protein species reflect the abundance of specific mRNAs and target gene systems associated with the disease state.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Specific brain protein changes correlated with behaviourally effective brain transplants.

The objective of this study was to identify cellular proteins that are associated with foetal brain transplants effective in reinstating memory function in adult rats with brain lesions. Quantitative memory deficits can be created in rats by lesioning the cholinergic projection system, using ibotenic acid. Previous work suggested that injection of cell suspensions prepared from presumptive cholinergic cells of foetal basal forebrain into adult brain, after such lesions, are most effective in restoring cognitive function. It was not clear, however, whether it was the cholinergic nature of the transplants that was critical for their success or whether other factors were involved. In this study, the proteins present in transplanted tissues and control brains were analysed by two-dimensional polyacrylamide gel electrophoresis to identify markers for the cells that were specifically correlated with restoration of cognitive function. On each gel, the relative optical densities of the same 33 selected proteins were measured on an interactive computerised image analyser. The amount of each protein was compared between treatment groups and correlated with four behavioural measurements. Seven of the proteins analysed had levels of expression that were either related to transplantation or correlated with behavioural performance. The proteins of interest were divided into the following three groups: (1) transplant-related proteins, (2) cholinergic transplant-specific proteins, and (3) behaviour-related proteins. Notable among the proteins of interest was one of the cholinergic transplant-specific proteins that was positively correlated with three of the four behavioural measurements and was also the only protein among those analysed that was significantly correlated with choline acetyltransferase (ChAT) levels. This has been identified, by immunoblotting, as glial fibrillary acidic protein, an astrocytic cell marker. These results suggest, therefore, that at least two cell types, astrocytes and ChAT(+)-staining cells, play an important role in the successful recovery of cognitive function. This study also identified possible protein markers for cognitive performance. The level of expression of two of the proteins analysed was not affected by lesioning or transplantation, but was significantly correlated with behaviour. One of these proteins, whose amounts correlated negatively with behavioural measurements, has been identified as neurone-specific enolase, a brain-specific neuronal cell marker.

Animals↗
PubMed1990

Low dose tetrahydroaminoacridine (THA) improves cognitive function but does not affect brain acetylcholine in rats.

Eight days of treatment with two low doses of tetrahydroaminoacridine (THA), given once daily, substantially improved radial maze performance in two groups of rats which showed persistent deficits either after ibotenic acid lesions at the source of forebrain cholinergic projections, or after 28 weeks treatment with alcohol (20% v/v) in drinking water. However, in immature, aged or aged and alcohol-treated rats, acetylcholine content was not significantly affected in any of the brain areas measured, even though the treatment regime had proved behaviourally effective. Inhibition of brain acetylcholinesterase activity was only marginally increased by this treatment regime. Thus, if THA influences behaviour by enhancing cholinergic transmission, its effects do not appear to be related to its activity as a cholinesterase inhibitor, and alternative mechanisms of action should be investigated.

Acetylcholine↗
PubMed1990

Reversible inhibition of acetylcholine synthesis and behavioural effects caused by 3-bromopyruvate.

3-Bromopyruvate inhibits pyruvate decarboxylase in brain homogenates and causes a 90% drop in acetylcholine tissue content at a concentration of 2 mM. Stereotaxic injection of 3-bromopyruvate into the basal forebrain causes after 7 days a 40% drop of acetylcholine concentration and pyruvate decarboxylase activity in the cortex and hippocampus, and greater decreases at the site of injection. However, values return to normal 18 days after injection. Choline acetyltransferase is partially inhibited only at the site of injection after 7 days. Choline transport and choline concentration are not affected at either 7 or 18 days after injection. Impairments in spontaneous alternation and in retention of passive avoidance were seen only 7 days after the injection. The results suggest that stereotaxic injection of bromopyruvate can induce discrete reversible cholinergic lesions on a time scale useful for behavioural experiments and for comparison with neurodegeneration.

Acetylcholine↗
PubMed1990

Exclusion of a schizophrenia susceptibility gene from the chromosome 5q11-q13 region: new data and a reanalysis of previous reports.

The report of a putative schizophrenia susceptibility gene linked to markers in the chromosome 5q11-q13 region and subsequent failures of replication have provoked considerable controversy. We here report six Welsh families multiply affected with schizophrenia in which there is no evidence for linkage between a dominant-like schizophrenia gene and 5q11-q13 markers. It is argued that our new results together with a combined reanalysis of previous studies suggest that a schizophrenia susceptibility gene can be excluded from the 5q11-q13 region. The apparent disparities between published results are most likely to reflect a chance finding in the one positive study and probably should not be interpreted as resulting from true linkage heterogeneity.

Chromosomes, Human, Pair 5↗
PubMed1989

Cholinergic system and memory in the rat: effects of chronic ethanol, embryonic basal forebrain brain transplants and excitotoxic lesions of cholinergic basal forebrain projection system.

Oral administration of ethanol (20% v/v) to male Sprague-Dawley rats for different periods of time up to 28 weeks resulted in profound reductions of acetylcholine content, in vitro synthesis and release of acetylcholine, choline uptake, activities of choline acetyltransferase, acetylcholinesterase and pyruvate decarboxylase, content of noradrenaline, serotonin and, to a lesser extent, dopamine throughout the brain. Changes were fully and partially reversible by a 4 weeks' ethanol-free period following a treatment of 8 and 18 weeks, respectively. They remained persistent, however, after 28 weeks of treatment. Performance in an eight arm-radial maze revealed a severe impairment in both spatial and non-spatial reference and working memory. A similar pattern of memory impairment was obtained after ibotenate lesion of the cholinergic basal forebrain projection system. In order to test whether this memory impairment depends on cholinergic deafferentation of the cortex, cholinergic-rich fetal basal forebrain cell suspensions were transplanted into cortex, hippocampus or both these sites in ethanol treated rats. Cholinergic-rich transplants, but not cholinergic-poor transplants, were effective in ameliorating impaired memory function and measures of cholinergic activity in the basal forebrain projection system. The behavioural efficacy of the basal forebrain grafts was well correlated with measures of both transplant volume and the degree to which they restored acetylcholine content at the transplant site; these transplants had no effect, however, on brain monoamine levels. The effects of the cholinergic-rich transplants into cortical and hippocampal sites were additive in their amelioration of performance in the radial maze. Similarly, ibotenate lesions of the sites of origin of the cholinergic projections to neocortex (in the region of the nucleus basalis magnocellularis) and hippocampus (the medial septal areas and nucleus of the diagonal band), respectively, were additive in their deleterious effects on maze performance. There were no qualitative differences in the susceptibility of the four different types of memory performance measured (spatial and non-spatial reference and working memory) to the effects of ethanol, ibotenate lesions of the cholinergic projection system, or cholinergic-rich brain tissue transplants. Thus, overall, the results indicate that the forebrain cholinergic system acts as a whole, without major functional differences between the projections originating in the medial septal area/diagonal band complex and the basal nucleus, and that it discharges a very general function in cognitive processes.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1988

Non-specific effects of the putative cholinergic neurotoxin ethylcholine mustard aziridinium ion in the rat brain examined by autoradiography, immunocytochemistry and gel electrophoresis.

Autoradiographic localisation of [3H]-ethylcholine mustard aziridinium ion (ECMA) after microinjection into the rat striatum has revealed intracellular sequestration of the toxin by glial and endothelial cells; fewer neuronal cells were labelled. Intrastriatal injection of 200 pmol ECMA caused severe cavitation of the tissue, extensive gliosis and permanent damage to myelinated structures, as revealed by immunocytochemical detection of glial fibrillary acidic protein (GFAP) and myelin basic protein (MBP). These non-specific effects are in addition to ECMA's irreversible action on the choline carrier associated with cholinergic neurons, and only marginally protected by concomitant administration of the reversible choline transport inhibitor hemicholinium-3. They may instead be attributed to the powerful alkylating action that ECMA has on tissue proteins, as shown by fluorography of synaptosomal proteins treated with [3H]ECMA and separated by SDS-PAGE.

Animals↗