Clinical insight among persons with schizophrenia spectrum disorders treated with amisulpride, aripiprazole or olanzapine: a semi-randomised trial.

BACKGROUND: Antipsychotic treatment may improve clinical insight. However, previous studies have reported inconclusive findings on whether antipsychotics improve insight over and above the reduction in symptoms of psychosis. These studies assessed homogeneous samples in terms of stage of illness. Randomised studies investigating a mixed population of first- and multiepisode schizophrenia spectrum disorders might clarify this disagreement. METHODS: Our data were derived from a pragmatic, rater-blinded, semi-randomised trial that compared the effectiveness of amisulpride, aripiprazole and olanzapine. A sample of 144 patients with first- or multiepisode schizophrenia spectrum disorders underwent eight assessments during a 1-year follow-up. Clinical insight was assessed by item General 12 from the Positive and Negative Syndrome Scale (PANSS). We analysed latent growth curve models to test if the medications had a direct effect on insight that was over and above the reduction in total psychosis symptoms. Furthermore, we investigated whether there were differences between the study drugs in terms of insight. RESULTS: Based on allocation analysis, all three drugs were associated with a reduction in total psychosis symptoms in the initial phase (weeks 0-6). Amisulpride and olanzapine were associated with improved insight over and above what was related to the reduction in total psychosis symptoms in the long-term phase (weeks 6-52). However, these differential effects were lost when only including the participants that chose the first drug in the randomisation sequence. We found no differential effect on insight among those who were antipsychotic-naïve and those who were previously medicated with antipsychotics. CONCLUSIONS: Our results suggest that antipsychotic treatment improves insight, but whether the effect on insight surpasses the effect of reduced total psychosis symptoms is more uncertain. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT01446328, 05.10.2011.

Impact of childhood trauma on antipsychotic effectiveness in schizophrenia spectrum disorders: A prospective, pragmatic, semi-randomized trial.

Antipsychotic medications are generally effective in ameliorating psychotic symptoms in schizophrenia spectrum disorders (SSDs). Identifying predictors associated with poor treatment response is important for a personalized treatment approach. Childhood trauma (CT) may have a general and differential effect on the effectiveness of different types of antipsychotics in SSDs. The Bergen-Stavanger-Trondheim-Innsbruck (BeSt InTro) study is a pragmatic, researcher-initiated, semi-randomized trial. The present study aimed to investigate symptom change (the Positive and Negative Syndrome Scale) from baseline to 1, 3, 6, 12, 26, 39 and 52 weeks of antipsychotic treatment (amisulpride, aripiprazole and olanzapine) by group (CT/no CT). Participants (n = 98) with diagnoses within the schizophrenia spectrum (F20-29 in the International Classification of Diseases - 10th Revision) were randomized to receive amisulpride, aripiprazole or olanzapine, and for this study categorized into groups of none and low CT, and moderate to severe CT according to thresholds defined by the Childhood Trauma Questionnaire Short-Form manual. CT in SSDs predicted an overall slower treatment response and less antipsychotic effectiveness after 26 weeks of treatment, which was statistically nonsignificant at 52 weeks. Secondary analyses showed a differential effect of CT related to type of antipsychotic medication: patients with SSDs and CT who received olanzapine showed less antipsychotic effectiveness throughout 52 weeks of treatment. The intention-to-treat and per-protocol analyses were convergent. Our findings indicate that in patients with SSD and CT, delayed response to antipsychotics could be expected, and a longer evaluation period before considering change of medication may be recommended.

First report of successful isolation of a HPR0-like variant of the infectious salmon anaemia virus (ISAV) using cell culture.

ISAV is the causative agent of the infectious salmon anaemia (ISA), a disease listed by the OIE that has caused important economic losses to the Atlantic salmon (Salmo salar) industry. ISAV variants are identified as pathogenic or non-pathogenic based on the presence or absence of a deletion in the highly polymorphic region (HPR) of segment 6 (S6). HPRΔ variants (pathogenic) are the only forms of the virus known to grow in cell culture. This is the first report of a HPR0 variant isolated in cell culture. The isolate is, however, atypical as it shows a marker of virulent variants on another segment (S5), which has never been reported for any other HPR0 variants. The significance of this finding remains unclear until more in-depth work is carried out but does challenge current knowledge.

Does childhood trauma influence cognitive functioning in schizophrenia? The association of childhood trauma and cognition in schizophrenia spectrum disorders.

Childhood trauma (CT) is a risk factor for schizophrenia spectrum disorders (SSDs), and cognitive impairment is a core feature and a vulnerability marker of SSDs. Studies of the relationship between CT and cognitive impairment in SSDs are inconclusive. In addition, few studies have examined differential effects of CT subtypes, e.g. physical, sexual or emotional abuse/neglect, on cognitive functioning. The present study therefore aimed to examine the effects of CT and CT subtypes on cognitive impairment in SSD. Participants (n = 78) with SSDs completed a comprehensive neuropsychological test battery and the Childhood Trauma Questionnaire Short-Form (CTQ-SF). We compared global cognitive performance as well as scores in seven subdomains (verbal abilities, visuospatial abilities, learning, memory, attention/working memory, executive abilities and processing speed) between participants reporting no CT and those reporting CT experiences using independent samples t-tests as well as linear regression analyses to control for possible confounders. CT subtype physical neglect was associated with attention and working memory after controlling for positive and negative psychosis symptoms, years of education, antipsychotics, gender and age, and adjustment of multiple testing. Our results indicate that the observed heterogeneity in cognitive impairment in SSDs, especially attention/working memory abilities, may in part be associated with childhood physical neglect.

A platform for x-ray Thomson scattering measurements of radiation hydrodynamics experiments on the NIF.

We present an experimental design for a radiation hydrodynamics experiment at the National Ignition Facility that measures the electron temperature of a shocked region using the x-ray Thomson scattering technique. Previous National Ignition Facility experiments indicate a reduction in Rayleigh-Taylor instability growth due to high energy fluxes, compared to the shocked energy flux, from radiation and electron heat conduction. In order to better quantify the effects of these energy fluxes, we modified the previous experiment to allow for non-collective x-ray Thomson scattering to measure the electron temperature. Photometric calculations combined with synthetic scattering spectra demonstrate an estimated noise.

Trajectories of depressive symptoms in the acute phase of psychosis: Implications for treatment.

Depression is common in schizophrenia and associated with negative outcomes. Previous studies have identified heterogeneity in treatment response in schizophrenia. We aimed to investigate different trajectories of depression in patients suffering from psychosis and predictors of change in depressive symptoms during antipsychotic treatment. Two hundred and twenty-six patients >18 years acutely admitted due to psychosis were consecutively included and the follow-up was 27 weeks. The Calgary Depression Scale for Schizophrenia (CDSS) sum score was the primary outcome. Latent growth curve (LGCM) and Growth Mixture Models (GMM) were conducted. Predictors were the Positive sum score of the Positive and Negative Syndrome Scale for Schizophrenia (PANSS), Schizophrenia spectrum/non-spectrum psychoses, gender and being antipsychotic naive at inclusion. We found support for three depression-trajectories, including a high- (14.7%), a low depression-level (69.6%) class and a third depressed class quickly decreasing to a low level (15.7%). Change in CDSS was associated with change in PANSS positive score in all time intervals (4 weeks: b = 0.18, p < 0.001, 3 months: 0.21, p < 0.023, 6 months: 0.43, p < 0.001) and with a diagnosis within schizophrenia spectrum but not with antipsychotic naivety or gender. The schizophrenia-spectrum patients had less depressive symptoms at inclusion (-2.63, p < 0.001). In conclusion, an early responding and a treatment refractory group were identified. The treatment-refractory patients are candidates for enhanced anti-depressive treatment, for which current evidence is limited. The post-psychotic depression group was characterized by depressive symptoms in the acute phase as well. We could not identify differentiating characteristics of the depression trajectories.

Using the cavitation collapse time to indicate the extent of histotripsy-induced tissue fractionation.

Histotripsy is an ultrasonic tissue ablation method based on acoustic cavitation. It has been shown that cavitation dynamics change depending on the mechanical properties of the host medium. During histotripsy treatment, the target-tissue is gradually fractionated and eventually liquefied to acellular homogenate. In this study, the change in the collapse time (t col) of the cavitation bubble cloud over the course of histotripsy treatment is investigated as an indicator for progression of the tissue fractionation process throughout treatment. A 500 kHz histotripsy transducer is used to generate single-location lesions within tissue-mimicking agar phantoms of varying stiffness levels as well as ex vivo bovine liver samples. Cavitation collapse signals are acquired with broadband hydrophones, and cavitation is imaged optically using a high-speed camera in transparent tissue-mimicking phantoms. The high-speed-camera-acquired measurements of t col validate the acoustic hydrophone measurements. Increases in t col are observed both with decreasing phantom stiffness and throughout histotripsy treatment with increasing number of pulses applied. The increasing trend of t col throughout the histotripsy treatment correlates well with the progression of lesion formation generated in tissue-mimicking phantoms (R 2 = 0.87). Finally, the increasing trend of t col over the histotripsy treatment is validated in ex vivo bovine liver.

Surviving 10 years with deep brain stimulation for Parkinson's disease--a follow-up of 79 patients.

BACKGROUND AND PURPOSE: Deep brain stimulation (DBS) for severe Parkinson's disease (PD) outperforms the best medical treatment in controlling motor symptoms and improving quality of life. Nevertheless disease progression cannot be controlled, and the development of dementia over time is nearly inevitable, often resulting in nursing home placement. Ten-year survival, development of hallucinations, dementia and nursing home placement were examined and adverse events were assessed. METHOD: Patient files were scrutinized from baseline up to 10 years of treatment or death on all 79 PD patients treated with DBS of the subthalamic nucleus from 1998 to 2003 at Aarhus University Hospital. RESULTS: Twenty-four patients died during the follow-up period of 10 years. Age above 60 years at surgery increased mortality 2.3-fold (P = 0.04). Of the 55 surviving patients 29 (53%) were demented and 19 (35%) were in nursing homes. Average time from operation to dementia was 5.6 ± 2.9 years. Hallucinations and nursing home placement were associated with increased mortality. CONCLUSION: Survival of 70% after a mean of 25 years of PD including 10 years with DBS illustrates that this is a selected group of PD patients. The prevalence of dementia steadily increased after surgery as expected from disease progression and can be an early event. Compared with the few similar long-term studies, the present study presents a larger cohort followed at the same DBS center for a longer period of time and none was lost to follow-up, making conclusions more valid. The present findings are of significant prognostic help for the patient, caregiver and physician when treatment with DBS has to be decided.

Suicidality in schizophrenia spectrum disorders: the relationship to hallucinations and persecutory delusions.

BACKGROUND: Assessment of suicide risk is crucial in schizophrenia and results concerning risk contributed by hallucinations and persecutory delusions are inconsistent. We aimed to determine factors associated with suicidal ideation and plans at the time of acute admission in patients suffering from schizophrenia spectrum disorders. METHODS: One hundred and twenty-four patients older than 18 years admitted to an acute psychiatric ward due to psychosis were consecutively included. Predictors of suicidal ideation and suicide plans at the time of admission were examined with multinominal logistic regression and structural equation modelling (SEM). The study design was pragmatic, thus entailing a clinically relevant representation. RESULTS: Depression Odds Ratio (OR) 12.9, Drug use OR 4.07, Hallucinations OR 2.55 and Negative symptoms OR 0.88 significantly predicted Suicidal ideation. Suspiciousness/ Persecution did not. Only Depression and Hallucinations significantly predicted Suicide plans. In the SEM-model Anxiety, Depression and Hopelessness connected Suspiciousness/Persecution, Hallucinations and Lack of insight with Suicidal ideation and Suicide plans. CONCLUSIONS: The study contributes to an increasing evidence base supporting an association between hallucinations and suicide risk. We want to emphasise the importance of treating depression and hallucinations in psychotic disorders, reducing hopelessness while working with insight and reducing drug abuse in order to lower suicide risk. TRIAL REGISTRATION: ClinicalTrials.gov ID; URL: http://www.clinicaltrials.gov/NCT00932529.

Numerical modeling of bubble dynamics in viscoelastic media with relaxation.

Cavitation occurs in a variety of non-Newtonian fluids and viscoelastic materials. The large-amplitude volumetric oscillations of cavitation bubbles give rise to high temperatures and pressures at collapse, as well as induce large and rapid deformation of the surroundings. In this work, we develop a comprehensive numerical framework for spherical bubble dynamics in isotropic media obeying a wide range of viscoelastic constitutive relationships. Our numerical approach solves the compressible Keller-Miksis equation with full thermal effects (inside and outside the bubble) when coupled to a highly generalized constitutive relationship (which allows Newtonian, Kelvin-Voigt, Zener, linear Maxwell, upper-convected Maxwell, Jeffreys, Oldroyd-B, Giesekus, and Phan-Thien-Tanner models). For the latter two models, partial differential equations (PDEs) must be solved in the surrounding medium; for the remaining models, we show that the PDEs can be reduced to ordinary differential equations. To solve the general constitutive PDEs, we present a Chebyshev spectral collocation method, which is robust even for violent collapse. Combining this numerical approach with theoretical analysis, we simulate bubble dynamics in various viscoelastic media to determine the impact of relaxation time, a constitutive parameter, on the associated physics. Relaxation time is found to increase bubble growth and permit rebounds driven purely by residual stresses in the surroundings. Different regimes of oscillations occur depending on the relaxation time.

Neurocognitive effectiveness of quetiapine, olanzapine, risperidone, and ziprasidone: a pragmatic, randomized trial.

PURPOSE: Cognitive effects of second generation antipsychotics (SGAs) are indicated in efficacy studies but the generalizability of the results may be limited by rigid designs and selected samples. The aim of this naturalistic, industry-independent study is to investigate whether differential neurocognitive effectiveness can be found among olanzapine, quetiapine, risperidone, and ziprasidone in a clinically relevant sample with psychosis. SUBJECTS AND METHODS: Adult patients acutely admitted to an emergency ward for psychosis were randomized to risperidone, olanzapine, quetiapine or ziprasidone and followed for up to 2 years. Participants were assessed repeatedly using the Positive and Negative Syndrome Scale and a repeatable neurocognitive test battery. RESULTS: A total of 226 patients were included and 171 patients underwent neurocognitive assessments. The sample had a global cognitive performance score at baseline about one standard deviation below that of the general population. The ziprasidone group had the fastest increase in global functioning which was significantly superior to that of the olanzapine group for the entire follow-up period. Before 90 days, the quetiapine group had the fastest increase which was statistically superior to the olanzapine group. DISCUSSION: Ziprasidone and quetiapine demonstrated superiority to olanzapine in increasing global neurocognitive performance in this naturalistic sample.

Time-dependent effect analysis of antipsychotic treatment in a naturalistic cohort study of patients with schizophrenia.

OBJECTIVE: Evidence based treatment of schizophrenia as well as antipsychotic drug utility patterns have changed considerably in recent years and the present study aims to investigate the current level of unplanned hospital readmissions in a cohort of patients with schizophrenia, and to determine the risk-reducing effects of current antipsychotic drug treatment. METHOD: An open cohort study included all consecutively discharged patients with schizophrenia in a 3-year period (n=277). The treatment-dependent variables were entered in a multivariate Cox survival analyses with time to unplanned readmission as the dependent variable. RESULTS: 11.2% of patients were readmitted within 30 days of discharge, and 44.8% were readmitted within 12 months. Antipsychotic monotherapy reduced the risk of readmission by 74.9%. Treatment in CMHC also had a risk-reducing effect. The prescription rate of clozapine in this sample was 10.1%. DISCUSSION: The over-all level of unplanned readmissions was in correspondence with the findings of others. Current antipsychotic drug treatment independently offers strong protection against unplanned readmissions. There may be a potential for further optimalizing antipsychotic drug treatment according to treatment guidelines. CONCLUSIONS: Unplanned readmissions are very common for patients with schizophrenia but antipsychotic drug treatment is associated with a strong risk-reducing effect in this regard.

MRI verified STN stimulation site--gait improvement and clinical outcome.

BACKGROUND: Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is effective in alleviating Parkinson's disease (PD) symptoms (tremor, rigidity and bradykinesia) and may improve gait and postural impairment associated with the disease. However, improvement of gait is not always as predictable as the clinical outcome. This may relate to the type of gait impairment or localization of the active DBS contact. METHODS: The active contact was visualized on peri-operative magnetic resonance imaging in 22 patients with idiopathic PD, consecutively treated with bilateral STN DBS. Stimulation site was grouped as either in the dorsal/ventral STN or medial/lateral hereof and anterior/posterior STN or medial/lateral hereof. The localization was compared with relative improvement of clinical outcome (UPDRS-III). In 10 patients, quantitative gait analyses were performed, and the improvement in gait performance was compared with stimulation site in the STN. RESULTS: Of 44 active contacts, 77% were inside the nucleus, 23% were medial hereof. Stimulation of the dorsal half improved UPDRS-III significantly more than ventral STN DBS (P = 0.02). However, there were no differences between anterior and posterior stimulation in the dorsal STN. Step velocity and length improved significantly more with dorsal stimulation compared with ventral stimulation (P = 0.03 and P = 0.02). Balance during gait was also more improved with dorsal stimulation compared with ventral stimulation. CONCLUSIONS: Deep brain stimulation of the dorsal STN is superior to stimulation of the ventral STN. Possible different effects of stimulation inside the nucleus underline the need for exact knowledge of the active stimulation site position to target the most effective area.

Comparative virulence of Infectious salmon anaemia virus isolates in Atlantic salmon, Salmo salar L.

Infectious salmon anaemia virus (ISAV) surveillance in the Bay of Fundy has identified the existence of a large number of genetically distinct ISAV isolates which appear to be of variable virulence. Genetically distinct isolates are currently being designated based on sequencing of the hyper polymorphic region (HPR) of genomic segment 6, which encodes the haemagglutinin-esterase protein, but it has been difficult to elucidate a clear association between these molecular variations and variations in virulence. This has hampered the establishment of proactive management decisions regarding infected fish, and ISAV infections, regardless of type, must be treated as one. Field data of ISAV infections is difficult to collect and to compare between infections because of a wide range of confounding factors including time of year, fish stock, cage site location, mitigating factors and stressors. An important tool in determining the relationship between molecular differences and virulence comes from analysis of quarantine studies. The goal of this study was to compare the virulence, by co-habitation and intraperitoneal injection, of four regionally common and recent ISAV isolates in a controlled environment. We found significant differences in mortality between ISAV molecular isolates, and present data showing that survival of ISAV infection confers significant resistance to re-infection with a different ISAV isolate. These findings, if borne out in field studies, will significantly alter the way ISAV infections are managed in the Bay of Fundy and elsewhere.

Practice regarding antipsychotic therapy: a cross-sectional survey in two Norwegian hospitals.

Since the introduction of chlorpromazine, an increasing number of drugs have been added to the list of antipsychotics (neuroleptics). These drugs can be further classified as either first-generation antipsychotics (FAPs) or second-generation antipsychotics (SAPs), depending on their ability to antagonize serotonine in addition to dopamine. The efficacy of various drugs is generally equal, whereas both pharmacological profiles and side-effects differ. Antipsychotic drug therapy recommendations are available both in Norway and internationally, and the purpose of this cross-sectional survey was to register the use of these drugs in representative mental hospitals (A and B), and compare our findings to the recommendations. Medical prescriptions were registered, and data further analysed. In hospital A, a total of 149 patients' prescriptions were registered. Antipsychotics were received voluntarily by 117 patients. Eighty-two of these used one antipsychotic drug, and in this group, 65% received SAPs. Antipsychotic combination therapy was received by 35 patients, and was associated with higher prescription rates of both anticholinergics and benzodiazepines. SAPs were not associated with increased use of benzodiazepines, compared to FAPs. Antipsychotics were frequently combined with mood stabilizers and antidepressants. Our findings in hospital A concerning therapy practices of antipsychotics, were confirmed in hospital B, where 64 patients' medical prescriptions were registered. We conclude that FAPs are still commonly prescribed. Antipsychotic combination therapy is used despite of lack of evidence for efficacy, and is associated with increased prescription rates of anticholinergics and benzodiazepines.

Some chemical properties of monochlorogallane: decomposition to gallium(I) trichlorogallate(III), Ga(+)[GaCl3H](-), and other reactions.

Thermal decomposition of monochlorogallane, [H2GaCl]n, at ambient temperatures releases H2 and results in the formation of gallium(I) species, including the new compound Ga[GaHCl3], which has been characterized crystallographically at 100 K (monoclinic P2(1)/n, a = 5.730(1), b = 6.787(1), c = 14.508(1) A, beta = 97.902(5) degrees ) and by its Raman spectrum. The gallane suffers symmetrical cleavage of the Ga(mu-Cl)2Ga bridge in its reaction with NMe3 but unsymmetrical cleavage, giving [H2Ga(NH3)2](+)Cl(-), in its reaction with NH3. Ethene inserts into the Ga-H bonds to form first [Et(H)GaCl]2 and then [Et2GaCl]2.

Preparation and properties of gallaborane, GaBH(6): structure of the gaseous molecule H(2)Ga(mu-H)(2)BH(2) as determined by vibrational, electron diffraction, and ab initio studies, and structure of the crystalline solid at 110 K as determined by X-ray diffraction.

Gallaborane (GaBH(6), 1), synthesized by the metathesis of LiBH(4) with [H(2)GaCl](n) at ca. 250 K, has been characterized by chemical analysis and by its IR and (1)H and (11)B NMR spectra. The IR spectrum of the vapor at low pressure implies the presence of only one species, viz. H(2)Ga(mu-H)(2)BH(2), with a diborane-like structure conforming to C(2v) symmetry. The structure of this molecule has been determined by gas-phase electron diffraction (GED) measurements afforced by the results of ab initio molecular orbital calculations. Hence the principal distances (r(alpha) in A) and angles ( angle(alpha) in deg) are as follows: r(Ga.B), 2.197(3); r(Ga-H(t)), 1.555(6); r(Ga-H(b)), 1.800(6); r(B-H(t)), 1.189(7); r(B-H(b)), 1.286(7); angleH(b)-Ga-H(b), 71.6(4); and angleH(b)-B-H(b), 110.0(5) (t = terminal, b = bridging). Aggregation of the molecules occurs in the condensed phases. X-ray crystallographic studies of a single crystal at 110 K reveal a polymeric network with helical chains made up of alternating pseudotetrahedral GaH(4) and BH(4) units linked through single hydrogen bridges; the average Ga.B distance is now 2.473(7) A. The compound decomposes in the condensed phases at temperatures exceeding ca. 240 K with the formation of elemental Ga and H(2) and B(2)H(6). The reactions with NH(3), Me(3)N, and Me(3)P are also described.

Contributions of imagery ability to stress and relaxation.

This study examined the contribution of imagery ability to psychological and physiological responses to stress and relaxation. Individuals (N = 176) participated in two study sessions. In the first session, participants completed the Creative Imagination Scale and were block-randomized to a stress or relaxation condition based on imaging scores. During the second session, stress and mood were assessed before and after participants watched a stressful movie or listened to a relaxation tape. Finger temperature was monitored during the interventions. Changes in temperature and in self-reports of stress and mood indicated that the manipulations were effective. In comparison to low imagers, high imagers reported greater stress after the movie and less stress and negative affect after the relaxation tape. Imagery ability predicted neither levels of negative affect following the stress condition nor changes in positive affect or temperature during the interventions. In the stress condition, expectations of stress partially mediated the relation between imagery ability andpsychological stress. In contrast, expectations of relaxation did not significantly predict responses to the relaxation intervention. These findings suggest that imagery ability is related to greater subjective responses to both stress and relaxation and that, in stressful situations, expectancies may account for some of the effects of imagery ability on perceived stress.

The level of the mitochondrial mutation A3243G decreases upon ageing in epithelial cells from individuals with diabetes and deafness.

We have in a longitudinal study determined the proportion of the mitochondrial A3243G mutation in DNA obtained from cervical cell samples collected from three individuals affected with mitochondrial diabetes and hearing loss during a period of up to 18 years. Using the minisequencing method we were able to sensitively determine the proportion between mutant and normal mitochondrial DNA. Our results demonstrate a constant decrease in the levels of the pathogenic mutation in mitotic tissues of affected individuals with time.

Monochlorogallane: physical properties and structure of the gaseous molecule H2Ga(mu-Cl)2GaH2 as determined by vibrational, electron diffraction, and ab initio studies.

Monochlorogallane, synthesized by the metathesis of gallium(III) chloride with an excess of trimethylsilane at ca. 250 K, has been characterized by chemical analysis, by its IR, Raman, and 1H NMR spectra, and by the products of its reaction with trimethylamine. The vibrational spectra of the vapor species isolated in solid Ar, N2, or CH4 matrixes at ca. 12 K imply the presence of only one species, viz. the dimer with an equilibrium structure conforming to D2h symmetry. The structure of this molecule has been determined by gas-phase electron diffraction (GED) measurements augmented by the results of ab initio molecular orbital calculations. An equilibrium structure with D2h symmetry has been assumed in the analysis of the electron diffraction pattern. However, as the molecule has a very low frequency Ga(mu-Cl)2Ga ring-puckering mode, a dynamic model was used to describe it with the aid of a set of pseudoconformers spaced at even intervals (deltadelta = 5 degrees, deltamax, = 20 delta) around the ring-puckering angle delta and Boltzmann-weighted according to a quartic potential V(delta) = V4delta4 + V2delta2. The differences in bond distances and angles between the different pseudoconformers were constrained to the values derived from the ab initio calculations employing second-order Moller-Plesset (MP2) methods (with all the electrons included in the correlation calculations) and a 6-311G(d) basis set. The results for the weighted average of the principal distances (ralpha) and angles (