D1 dopamine receptor--the search for a function: a critical evaluation of the D1/D2 dopamine receptor classification and its functional implications

The present review focuses on the hypothesized D1/D2 dopamine (DA) receptor classification, originally based on the form of receptor coupling to adenylate cyclase activity. The pharmacological effects of compounds exhibiting putative selective agonist or antagonist profiles at those DA receptors positively coupled to adenylate cyclase activity (D1 DA receptors) are extensively reviewed. Comparisons are made with the effects of putative selective D2 DA receptor agonists and antagonists, and on the basis of this work, the DA receptor classification is critically evaluated. A variety of biochemical, behavioral, and electrophysiological evidence is presented which supports the view that D1 and D2 DA receptors can interact in both an opposing and synergistic fashion. Particular attention is focused on the possibility that D1 receptor stimulation is required to enable the expression of certain D2 receptor-mediated effects, and the functional consequences of this form of interaction are considered. A hypothetical model is presented which considers how both the opposing and enabling forms of interaction between D1 and D2 DA receptors can control behavioral expression. Finally, the clinical relevance of this work is discussed and the potential use of selective D1 receptor agonists and antagonists in the treatment of psychotic states and Parkinson's disease is considered.

Virtual reality in the assessment, understanding, and treatment of mental health disorders

Mental health problems are inseparable from the environment. With virtual reality (VR), computer-generated interactive environments, individuals can repeatedly experience their problematic situations and be taught, via evidence-based psychological treatments, how to overcome difficulties. VR is moving out of specialist laboratories. Our central aim was to describe the potential of VR in mental health, including a consideration of the first 20 years of applications. A systematic review of empirical studies was conducted. In all, 285 studies were identified, with 86 concerning assessment, 45 theory development, and 154 treatment. The main disorders researched were anxiety (n = 192), schizophrenia (n = 44), substance-related disorders (n = 22) and eating disorders (n = 18). There are pioneering early studies, but the methodological quality of studies was generally low. The gaps in meaningful applications to mental health are extensive. The most established finding is that VR exposure-based treatments can reduce anxiety disorders, but there are numerous research and treatment avenues of promise. VR was found to be a much-misused term, often applied to non-interactive and non-immersive technologies. We conclude that VR has the potential to transform the assessment, understanding and treatment of mental health problems. The treatment possibilities will only be realized if - with the user experience at the heart of design - the best immersive VR technology is combined with targeted translational interventions. The capability of VR to simulate reality could greatly increase access to psychological therapies, while treatment outcomes could be enhanced by the technology's ability to create new realities. VR may merit the level of attention given to neuroimaging.

Burst firing in midbrain dopaminergic neurons

Midbrain dopaminergic (DA) neurons fire bursts of activity in response to sensory stimuli, including those associated with primary reward. They are therefore conditional bursters - the bursts conveying, amongst other things, motivationally relevant information to the forebrain. In the forebrain, bursts give rise to a supra-additive release of dopamine, and possibly favour the release of co-localised neuropeptides. Evidence is presented that in rat DA neurons, bursts are engendered by the activity of cortically-regulated afferents. Certain factors are identified which, in combination, lead to burst production: (1) A burst of activity in EAAergic afferents to DA neurons arising from non-cortical sources, but controlled by the medial prefrontal cortex; (2) N-methyl-D-aspartate receptor activation, producing a slow depolarising wave in the recipient neuron; (3) activation of a high threshold, dendritically located calcium conductance which produces a 'plateau potential'; (4) activation of a calcium-activated potassium conductance, which terminates the burst. These factors are argued to operate in the context of an 'optimal' level of intracellular calcium buffering for bursting. Other factors which appear to be involved in bursting in other systems, in particular a low threshold calcium conductance, are rejected as being necessary for bursting in DA neurons. The factors which do play a crucial role in burst production in DA neurons are integrated into a theory from which arises a series of hypotheses amenable to empirical investigation. Additional factors are discussed which may modulate bursting. These may either act indirectly through changes in membrane potential (or intracellular calcium concentration), or they may act directly through an interaction with certain conductances, which appear to promote or inhibit burst firing in DA neurons.

Epstein-Barr virus gene expression in nasopharyngeal carcinoma

Epstein-Barr virus (EBV), an agent with growth transforming potential for human B cells, is associated with certain B cell lymphomas in man and also with an epithelial tumour, undifferentiated nasopharyngeal carcinoma (NPC). Since B cell growth transformation is associated with the constitutive expression of a small number of EBV-coded latent proteins, the nuclear antigens EBNA 1, EBNA 2, EBNA 3 and EBNA-LP and the latent membrane protein (LMP), the present work sought to determine whether this same pattern of virus gene expression occurred in NPC. Tumour biopsies were taken from NPC patients from three areas of differing tumour incidence (Kenya, Algeria, Britain) and immediately snap-frozen, as were biopsies of non-EBV-related carcinomas for controls. Immunoblotting of PAGE-separated proteins with selected human sera identified 24 NPC biopsies clearly expressing EBNA 1. When the analysis was extended using selected human sera with antibodies against the other EBNAs, there was no detectable expression of EBNA 2, EBNA 3 or EBNA-LP in any of these 24 biopsies; their EBNA 2-negative status was confirmed using a monoclonal antibody (MAb) PE2 which was reactive in immunoblotting and in immunoprecipitation with EBNA 2A and EBNA 2B proteins. Similar experiments with two different LMP-specific MAbs, CS1 to 4 and S12, revealed heterogeneity between NPC biopsies; 9/24 biopsies were demonstrably LMP-positive, the degree of expression varying considerably between individual tumours in a manner which was not related to the level of EBNA 1 expression. None of the 24 NPC biopsies expressed detectable amounts of EBV lytic cycle antigens. A nude mouse-passaged NPC cell line, C15, likewise expressed EBNA 1 and LMP but none of the other EBV latent proteins nor lytic cycle antigens. This work identifies a novel type of EBV-cell interaction in NPC cells which is distinct from that seen in in vitro transformed B cell lines and from that seen to date in EBV-positive B cell lymphomas.

Assessment of function in routine clinical practice: description of the COOP Chart method and preliminary findings

The COOP Project, a primary care research network, has begun development of a Chart method to screen function quickly. The COOP Charts, analogous to Snellen Charts, were pretested in two practices on adult patients (N = 117) to test feasibility, clinical utility, and validity. Patients completed questionnaires containing validated health status scales and sociodemographic variables. Practice staff filled out forms indicating COOP Chart scores and clinical data. We held debriefing interviews with staff who administered the Charts. The results indicate the Charts take 1-2 minutes to administer, are easy to use, and produce important clinical data. The patterns of correlations between the Charts and validity indicator variables provide evidence for both convergent and discriminant validity. We conclude that new measures are needed to assess function in a busy office practice and that the COOP Chart system represents one promising strategy.

Systematic review of the problems and issues of accessing specialist palliative care by patients, carers and health and social care professionals

OBJECTIVES

To determine the problems and issues of accessing specialist palliative care by patients, informal carers and health and social care professionals involved in their care in primary and secondary care settings.

DATA SOURCES

Eleven electronic databases (medical, health-related and social science) were searched from the beginning of 1997 to October 2003. Palliative Medicine (January 1997-October 2003) was also hand-searched.

STUDY SELECTION

Systematic search for studies, reports and policy papers written in English.

DATA EXTRACTION

Included papers were data-extracted and the quality of each included study was assessed using 10 questions on a 40-point scale.

RESULTS

The search resulted in 9921 hits. Two hundred and seven papers were directly concerned with symptoms or issues of access, referral or barriers and obstacles to receiving palliative care. Only 40 (19%) papers met the inclusion criteria. Several barriers to access and referral to palliative care were identified including lack of knowledge and education amongst health and social care professionals, and a lack of standardized referral criteria. Some groups of people failed to receive timely referrals e.g., those from minority ethnic communities, older people and patients with nonmalignant conditions as well as people that are socially excluded e.g., homeless people.

CONCLUSIONS

There is a need to improve education and knowledge about specialist palliative care and hospice care amongst health and social care professionals, patients and carers. Standardized referral criteria need to be developed. Further work is also needed to assess the needs of those not currently accessing palliative care services.

'Total pain', disciplinary power and the body in the work of Cicely Saunders, 1958-1967

Pain first emerged as an area of clinical specialisation in the 1950s, but more recently has attracted wider interest from social scientists and clinicians who seek to expand its understanding to incorporate ideas about meaning, embodiment and culture. So far there have been few empirical studies which focus on how ideas and practices about pain are changing in modern healthcare. This paper addresses these issues through a specific case study of the early writings of Cicely Saunders in the period 1958-1967. A professional training in the three disciplines of nursing, social work and medicine, coupled with a strong personal religious faith, provided the biographical context for the development of Cicely Saunders' concern with pain. Through these influences we find in her work with dying patients an emphasis on pain as a key which unlocks other problems and as something which requires multiple interventions for its resolution. From here the concept of 'total pain' is formulated, to include physical, psychological, social, emotional and spiritual elements. This concept, which proved so important to the development of hospice clinical practice, is shown to have paradoxical and conflicting implications. Adopting current ideas about the social theory of the body, 'total pain' may be formulated either as a nomenclature of inscription, or as a nomenclature of facilitation. It is suggested that both of these may be at work in the discourse of 'total pain' and that an appreciation of each enhances our understanding of the concept.

Dengue type 4 virus mutants containing deletions in the 3' noncoding region of the RNA genome: analysis of growth restriction in cell culture and altered viremia pattern and immunogenicity in rhesus monkeys

The dengue type 4 virus (DEN4) genome contains a 384-nucleotide (nt) 3' noncoding sequence in which the last 81 nt, predicted to form a secondary structure, are thought to be essential for virus replication. Immediately upstream of the secondary structure, short RNA sequences that are conserved among mosquito-borne flaviviruses have been identified. A series of deletions that range from 30 to 262 nt were introduced into this upstream region of full-length DEN4 cDNA to create viable deletion mutants, some of which might prove to be useful for inclusion in a live attenuated virus vaccine. When studied by an infectious-center assay, most full-length RNA transcripts of the deletion constructs exhibited reduced infectivity when transfected into simian LLC-MK2 cells compared with the full-length RNA transcripts of wild-type parental virus. Deletion mutations that extended as far as the 5' boundary of the 3' noncoding region and whose 3' boundary did not extend beyond the last 113 nt of the 3' end were viable. With the exception of mutant 3'd 303-183, which contained a deletion of nt 303 to 183 from the 3' terminus, deletion mutants produced plaques that appeared late on simian LLC-MK2 cells or exhibited a small-plaque morphology on mosquito C6/36 cells compared with the wild-type virus. These mutants also replicated less efficiently and attained a lower titer in LLC-MK2 cells than parental wild-type virus. Significantly, mutant 3'd 303-183 grew to a high titer and was least restricted in growth. Mutant 3'd 303-183 and four other moderately to severely restricted mutants were selected for evaluation of infectivity and immunogenicity in rhesus monkeys. There was a suggestion that occurrence and duration of viremia were reduced for some of the deletion mutants compared with the wild-type virus. However, more convincing evidence for attenuation of some of the mutants was provided by an analysis of antibody response to infection. Mutant 3'd 303-183 induced an antibody response equivalent to that stimulated by wild-type virus, whereas other mutants induced low to moderate levels of antibodies, as measured by radioimmunoprecipitation and virus neutralization. The immunogenicity of these 3' DEN4 deletion mutants in monkeys appeared to correlate with their efficiency of growth in simian LLC-MK2 cells. One or more mutants described in this paper may prove to be useful for immunization of humans against disease caused by dengue virus.

Clinical predictors of suicide in patients with major affective disorders: a controlled prospective study

The authors report prospective uniform clinical data differentiating 25 patients who committed suicide from 929 patients who did not in a group of 954 patients with major affective disorder followed for an average of 4 years in the Collaborative Program on the Psychobiology of Depression. Eight (32%) of the suicides occurred within 6 months and 13 (52%) within 1 year of entry into the study. Hopelessness, loss of pleasure or interest, and mood cycling during the index episode differentiated the suicide group. Diagnostic subcategories, suicidal ideation at entry to the study, suicide attempts during current or past episodes, and medical severity of prior attempts did not differentiate the suicide group.

Immunoglobulin synthesis by lymphoid cells transformed in vitro by Abelson murine leukemia virus

The majority of cell lines derived by infection of murine bone marrow cells with Abelson murine leukemia virus (A-MuLV) synthesize a mu chain but no detectable light chain. Aside from this mu-only phenotype, lines that make only light chain, both chains or no immunoglobulin-related polypeptides have also been found. Two lines have been studied in detail: one that makes only mu chain and one that makes only kappa light chain. Synthesis of both polypeptides can be increased by modifying the culture conditions so as to decrease the growth rate of the cells. Although some kappa chain secretion was observed, neither secreted nor surface mu was detected. We suggest that the mu- only phenotype may be an early normal step in the pathway of B lymphocyte maturation.

Clinical characteristics with inflammation profiling of long COVID and association with 1-year recovery following hospitalisation in the UK: a prospective observational study

BACKGROUND

No effective pharmacological or non-pharmacological interventions exist for patients with long COVID. We aimed to describe recovery 1 year after hospital discharge for COVID-19, identify factors associated with patient-perceived recovery, and identify potential therapeutic targets by describing the underlying inflammatory profiles of the previously described recovery clusters at 5 months after hospital discharge.

METHODS

The Post-hospitalisation COVID-19 study (PHOSP-COVID) is a prospective, longitudinal cohort study recruiting adults (aged ≥18 years) discharged from hospital with COVID-19 across the UK. Recovery was assessed using patient-reported outcome measures, physical performance, and organ function at 5 months and 1 year after hospital discharge, and stratified by both patient-perceived recovery and recovery cluster. Hierarchical logistic regression modelling was performed for patient-perceived recovery at 1 year. Cluster analysis was done using the clustering large applications k-medoids approach using clinical outcomes at 5 months. Inflammatory protein profiling was analysed from plasma at the 5-month visit. This study is registered on the ISRCTN Registry, ISRCTN10980107, and recruitment is ongoing.

FINDINGS

2320 participants discharged from hospital between March 7, 2020, and April 18, 2021, were assessed at 5 months after discharge and 807 (32·7%) participants completed both the 5-month and 1-year visits. 279 (35·6%) of these 807 patients were women and 505 (64·4%) were men, with a mean age of 58·7 (SD 12·5) years, and 224 (27·8%) had received invasive mechanical ventilation (WHO class 7-9). The proportion of patients reporting full recovery was unchanged between 5 months (501 [25·5%] of 1965) and 1 year (232 [28·9%] of 804). Factors associated with being less likely to report full recovery at 1 year were female sex (odds ratio 0·68 [95% CI 0·46-0·99]), obesity (0·50 [0·34-0·74]) and invasive mechanical ventilation (0·42 [0·23-0·76]). Cluster analysis (n=1636) corroborated the previously reported four clusters: very severe, severe, moderate with cognitive impairment, and mild, relating to the severity of physical health, mental health, and cognitive impairment at 5 months. We found increased inflammatory mediators of tissue damage and repair in both the very severe and the moderate with cognitive impairment clusters compared with the mild cluster, including IL-6 concentration, which was increased in both comparisons (n=626 participants). We found a substantial deficit in median EQ-5D-5L utility index from before COVID-19 (retrospective assessment; 0·88 [IQR 0·74-1·00]), at 5 months (0·74 [0·64-0·88]) to 1 year (0·75 [0·62-0·88]), with minimal improvements across all outcome measures at 1 year after discharge in the whole cohort and within each of the four clusters.

INTERPRETATION

The sequelae of a hospital admission with COVID-19 were substantial 1 year after discharge across a range of health domains, with the minority in our cohort feeling fully recovered. Patient-perceived health-related quality of life was reduced at 1 year compared with before hospital admission. Systematic inflammation and obesity are potential treatable traits that warrant further investigation in clinical trials.

FUNDING

UK Research and Innovation and National Institute for Health Research.

In vivo measurement of extracellular 5-hydroxytryptamine in hippocampus of the anaesthetized rat using microdialysis: changes in relation to 5-hydroxytryptaminergic neuronal activity

The effect of manipulating the activity of central 5-hydroxytryptamine (5-HT) neurones on extracellular 5-HT in ventral hippocampus of the chloral hydrate-anaesthetized rat was studied using the brain perfusion method, microdialysis. Basal levels of 5-HT in the dialysates were close to the detection limits of our assay using HPLC with electrochemical detection. However, addition of the selective 5-HT reuptake inhibitor citalopram (10(-6) M) to the perfusion medium produced readily measurable amounts of dialysate 5-HT. Citalopram, therefore, was used throughout our experiments. Hippocampal dialysate levels of 5-HT sharply declined over the first hour after dialysis probe implantation, but then became constant. This stable output of 5-HT was reduced by 57% in rats treated 14 days previously with intracerebroventricular injections of the 5-HT neurotoxin 5,7-dihydroxytryptamine. Electrical stimulation (1-ms pulse width, 300 microA, 2-20 Hz) of the dorsal raphe nucleus for 20 min caused a rapid rise in hippocampal 5-HT output, which immediately declined on cessation of the stimulus and was frequency-dependent. Addition of tetrodotoxin (10(-6) M) to the perfusion medium reduced 5-HT levels to 75% of predrug values. Injection of the 5-HT1A agonist 8-hydroxy-2-(di-n-propylamino)tetralin (0.5 and 2.5 micrograms) into the dorsal raphe nucleus caused a dose-related fall in hippocampal output of 5-HT compared to saline-injected controls. We conclude from these data that the spontaneous output of endogenous 5-HT into hippocampal dialysates, measured under our experimental conditions, predominantly originates from central 5-HT neurones and changes in accordance with their electrical activity.

Proliferating cell nuclear antigen and Msh2p-Msh6p interact to form an active mispair recognition complex

Proliferating cell nuclear antigen (PCNA) is required for mismatch repair (MMR) and has been shown to interact with complexes containing Msh2p or MLH1 (refs 1-4). PCNA has been implicated to act in MMR before and during the DNA synthesis step, although the biochemical basis for the role of PCNA early in MMR is unclear. Here we observe an interaction between PCNA and Msh2p-Msh6p mediated by a specific PCNA-binding site present in Msh6p. An msh6 mutation that eliminated the PCNA-binding site caused a mutator phenotype and a defect in the interaction with PCNA. The association of PCNA with Msh2p-Msh6p stimulated the preferential binding of Msh2p-Msh6p to DNA containing mispaired bases. Mutant PCNA proteins encoded by MMR-defective pol30 alleles were defective for interaction with Msh2p-Msh6p and for stimulation of mispair binding by Msh2p-Msh6p. Our results suggest that PCNA functions directly in mispair recognition and that mispair recognition requires a higher-order complex containing proteins in addition to Msh2p-Msh6p.

Iontophoretically administered drugs acting at the N-methyl-D-aspartate receptor modulate burst firing in A9 dopamine neurons in the rat

Extracellular single-unit recording and iontophoresis were used to examine the effect of N-methyl-D-aspartate (NMDA) and the competitive NMDA antagonist (+/-)-4-(3-phosphonopropyl)-2-piperazine carboxylic acid (CPP) on the firing rate and firing pattern of A9 dopamine (DA) neurons in the rat. Administration of NMDA produced a dose-dependent increase in firing rate (up to nearly 300% of baseline at the highest ejection current), which could be blocked by iontophoretic CPP. Low currents (less than 10 nA) were sufficient to induce apparent depolarisation inactivation in some neurons. In addition to this effect on firing rate, NMDA also caused a dramatic increase in burst firing, which was also dose dependent; cells made more bursts, and each burst consisted of more spikes. The only measured aspect of burst morphology that was not affected was the mean burst interspike interval. All nonbursting cells (n = 10) were converted to burst firing by the drug. CPP administered alone was found to reduce burst firing, without affecting the firing rate. These data suggest that a tonically active excitatory amino acid input to A9 DA neurons is responsible for inducing burst firing in vivo and that this input seems to operate via the NMDA receptor, possibly by virtue of its link to a Ca2+ ionophore.

Central dopamine receptor agonist and antagonist actions of the enantiomers of 3-PPP

The two enantiomers of the putative centrally acting dopamine (DA) autoreceptor agonist 3-(3-hydroxyphenyl)-N-n-propylpiperidine, 3-PPP (Hjorth et al. 1981), were pharmacologically evaluated. An extensive series of biochemical and behavioural experiments unexpectedly revealed that both (+)- and (-)-3-PPP showed clear, but differential, effects on the DA receptors. Thus, (+)-3-PPP is a DA agonist with autoreceptor as well as postsynaptic receptor stimulatory properties. In contrast, although (-)-3-PPP similarly activates DA autoreceptors it acts concomitantly as an antagonist at postsynaptic DA receptors. Moreover, both behavioural and biochemical data on motor activity and DA synthesis and turnover suggest a preferential limbic action for the (-)-enantiomer. These results are discussed in terms of the dual antidopaminergic action of (-)-3-PPP coupled with anatomical differences in the feedback organisation in central (viz, limbic vs striatal) DA systems. It is suggested that compounds like (-)-3-PPP may be of potential clinical utility in the treatment of psychotic disorders, whilst lacking the seriously incapacitating motor dysfunctions produced by current neuroleptic therapy.

Place of death: preferences among cancer patients and their carers

The place of death of cancer patients has become an important theme in UK cancer and palliative care policy. This paper examines the place of death preferences of 41 terminally ill cancer patients and 18 of their informal carers, living in the Morecambe Bay area of north-west England. We interviewed cancer patients referred to the research team by 13 specialist palliative care professionals; patients had an estimated 3 months of life remaining. The study design involved an in-depth qualitative interview with each patient soon after referral to the study, followed by an interview some 4 weeks later and subsequent tracking interviews by telephone at 2-4 week intervals until death occurred. Interviews were also conducted with main coresident carers soon after patient referral to the study and again in the post-bereavement period. Thirteen factors were identified as shaping the place of death preference of patients and carers. These are organised into four thematic domains: the informal care resource, management of the body, experience of services, and existential perspectives. In documenting these factors, this paper adds significantly to current knowledge on the factors that shape place of death preference, a field of enquiry acknowledged to be underdeveloped (J. Palliative Med. 3 (2000) 287). More importantly, it uncovers some of the reasons that underpin these preferences. Our research revealed a much stronger preference for deaths in a hospice than had been anticipated, leading us to take a qualified stance on the current policy drive in favour of home deaths by those charged with delivering UK cancer and palliative care services.

Dopamine-receptor agonists: mechanisms underlying autoreceptor selectivity. I. Review of the evidence

The behavioural, biochemical, neuroendocrinological and electrophysiological actions of the enantiomers of the dopamine (DA) analogue 3-(3-hydroxyphenyl)-N-n-propylpiperidine, 3-PPP, are extensively reviewed. (+)-3-PPP acts in a fashion similar to classical direct-acting DA agonists, stimulating both DA autoreceptors and postsynaptic DA receptors, although in some situations the drug appears to exhibit partial agonist activity. (-)-3-PPP exerts a variety of actions in different pharmacological models. Either agonistic, antagonistic or both agonistic and antagonistic activity are observed depending on the anatomical location of the relevant DA receptors and the experimental conditions. The actions of transdihydrolisuride (TDHL) and the trans-fused 7-OH-1,2,3,4,4a,5,6,10b-octahydrobenzo(f)quinoline (HW 165) are also discussed. These agents possess a similar spectrum of action to (-)-3-PPP suggesting a new generation of DA agonists which exhibit variable intrinsic activity at different DA receptors. Finally, evidence is presented indicating that the 3-PPP enantiomers display selectivity for DA receptors.

Psychopathy and the predictive validity of the PCL-R: an international perspective

Its controversial past notwithstanding, psychopathy has emerged as one of the most important clinical constructs in the criminal justice and mental health systems. One reason for the surge in theoretical and applied interest in the disorder is the development and widespread adoption of reliable and valid methods for its measurement. The Hare PCL-R provides researchers and clinicians with a common metric for the assessment of psychopathy, and has led to a surge in replicable and meaningful findings relevant to the issue of risk for recidivism and violence, among other things. Most of the research thus far has been based on North American samples of offenders and forensic psychiatric patients. We summarize this research and compare it with findings from several other countries, including England and Sweden. We conclude that the ability of the PCL-R to predict recidivism, violence, and treatment outcome has considerable cross-cultural generalizability, and that the PCL-R and its derivatives play a major role in the understanding and prediction of crime and violence.

Epstein-Barr virus receptors on human pharyngeal epithelia

The apparently strict tropism of Epstein-Barr virus (EBV) for B lymphocytes has been attributed to the existence of a B-lineage-specific surface molecule, the C3d receptor, which also functions as a receptor for EBV. Two monoclonal antibodies against different determinants on the EBV/C3d receptor of B cells were shown to react with pharyngeal epithelia in a cell differentiation-dependent manner. These findings, which raise the possibility of direct virus entry into a naturally exposed epithelium, strengthen the evidence in favour of an epithelial reservoir of EBV infection in vivo and identify a means whereby the virus/epithelium interactions leading to nasopharyngeal carcinoma might be initiated.

Nitric oxide inhibition of tobacco catalase and ascorbate peroxidase

We used a variety of nitric oxide (NO) donors to demonstrate that NO inhibits the activities of tobacco catalase and ascorbate peroxidase (APX). This inhibition appears to be reversible because removal of the NO donor led to a significant recovery of enzymatic activity. In contrast, APX and catalase were irreversibly inhibited by peroxynitrite. The ability of NO and peroxynitrite to inhibit the two major H2O2-scavenging enzymes in plant cells suggests that NO may participate in redox signaling during the activation of defense responses following pathogen attack.

Stimulation of the prefrontal cortex in the rat induces patterns of activity in midbrain dopaminergic neurons which resemble natural burst events

Evidence suggests that excitatory amino acid-containing afferents from the prefrontal cortex (PFC) play an important role in the induction of burst firing in midbrain dopaminergic (DA) neurons. In the present study, the extracellular activity of individual DA neurons (A10 and A9 cell groups) was recorded during single pulse electrical stimulation (0.25 and 1 mA) of the PFC. The majority of cells were responsive, and two main patterns of activity were elicited: responses characterised by an initial excitation (E responses; 41.8% of responses at 0.25 mA and 26.6% at 1 mA; cell groups combined) and responses characterised by excitation following an initial inhibition (IE responses; 43.3% of responses at 0.25 mA and 56.6% at 1 mA; cell groups combined). Burst analysis performed on the excitatory phase of E and IE responses revealed that the excitation contained events which fulfilled the criteria for natural bursts in DA neurons. A procedure was developed for assessing whether these bursts were time-locked to the stimulus. This showed that 27.9% of E responses and 33.3% of IE responses were accompanied by time-locked bursts (currents and cell groups combined). It is argued that time-locked bursts during IE responses were produced by rebound activation of a low threshold calcium conductance, whereas time-locked bursts during E responses were produced by excitatory afferents. Since natural bursts in DA neurons also seem to involve cortically induced excitation, the hypothesis that the PFC plays a role in the production of natural bursts in DA neurons is strengthened.

Identification and catabolic activity of well-derived gasoline-degrading bacteria from a contaminated aquifer

Approximately 300 gasoline-degrading bacteria were isolated from well water and core material from a shallow coastal aquifer contaminated with unleaded gasoline. Identification of 244 isolates revealed four genera: Pseudomonas, Alcaligenes, Nocardia, and Micrococcus, with pseudomonads making up 86.9% of bacteria identified. A total of 297 isolates was sorted into 111 catabolic groups on the basis of aerobic growth responses on 15 gasoline hydrocarbons. Each test hydrocarbon was degraded by at least one isolate. Toluene, p-xylene, ethylbenzene, and 1,2,4-trimethylbenzene were most frequently utilized as growth substrates, whereas cyclic and branched alkanes were least utilized. Most isolates were able to grow on 2 or 3 different hydrocarbons, and nearly 75% utilized toluene as a sole source of carbon and energy. Isolates were remarkably specific for hydrocarbon usage, often catabolizing only one of several closely related compounds. A subset of 220 isolates was sorted into 51 groups by polyacrylamide gel electrophoresis. Pseudomonas aeruginosa was partitioned into 16 protein-banding groups (i.e., subspecies) whose catabolic activities were largely restricted to substituted aromatics. Different members of subspecies groups defined by protein-banding pattern analysis often exhibited different growth responses on the same hydrocarbon, implying marked strain diversity. The catabolic activities of well-derived, gasoline-degrading bacteria associated with this contaminated aquifer are consonant with in situ adaptation at the site.