Morphine and shuttle-box self-stimulation in the rat: a model for euphoria.

In a shuttle-box self-stimulation paradigm, analgesic doses of morphine increase the amount of time a rat leaves rewarding brain stimulation on, without altering average OFF times. This paradigm may serve as a model for the euphoria induced by narcotic drugs and as a useful tool for evaluating the reinforcing effects of drugs.

Explantation of fetal murine retinae to the chorioallantoic membrane of the chicken embryo.

A technique is here described for the culture of mammalian retinal explants on the chorioallantoic membrane of the developing chicken embryo. As an integral part of the central nervous system, the mammalian retina is characterised by its highly organised laminar structure and developmental timetable. Study of its prenatal development is, however, difficult to undertake in utero. In an attempt to render the organ of vision more accessible experimentally, fetal mouse retinae were explanted across major species barriers to the live chorioallantoic membrane of the chick. From 26 experiments, 128 explants (70% of the total) were recovered and 27 possessed a cytomorphology apparently identical to that of age-matched controls. The surviving retinae were analysed using a specifically devised set of criteria and they had developed a normal laminar structure (ganglion cell, inner plexiform, inner nuclear, outer plexiform and outer nuclear layers) but increased numbers of pyknotic profiles were present and somal sizes in the ganglion cell layer were significantly smaller. Such patterns have been obtained in other studies, both in vivo and in vitro, in which retinae had no access to their major targets in the brain, the superior colliculus and lateral geniculate nucleus. Explantation to the chorioallantoic membrane is thus a viable alternative for experiments requiring tissue isolation from natural surroundings since the explants are accessible for manipulation and observation while interacting with the host chick embryo. Furthermore, the technique allows examination of retinal differentiation, offering the opportunity to answer a number of important questions regarding development in the central nervous system.

Etorphine and shuttle-box self-stimulation in the rat.

Rats were trained to turn rewarding electrical brain stimulation on and off by crossing back and forth in a shuttle-box. Moderate doses of the narcotic analgesic, etorphine, increased mean ON times while having little effect on OFF times. Tolerance did not develop to the reward enhancement action over five consecutive days of injections. This paradigm seems valuable for exploration of the reinforcing properties of narcotic drugs.

Longitudinal changes in magnetisation transfer ratio in secondary progressive multiple sclerosis: data from a randomised placebo controlled trial of lamotrigine.

Sodium blockade with lamotrigine is neuroprotective in animal models of central nervous system demyelination. This study evaluated the effect of lamotrigine on magnetisation transfer ratio (MTR), a putative magnetic resonance imaging measure of intact brain tissue, in a group of subjects with secondary progressive multiple sclerosis (MS). In addition, the utility of MTR measures for detecting change in clinically relevant pathology was evaluated. One hundred seventeen people attending the National Hospital for Neurology and Neurosurgery or the Royal Free Hospital, London, UK, were recruited into a double-blind, parallel-group trial. Subjects were randomly assigned by minimisation to receive lamotrigine (target dose 400 mg/day) or placebo for 2 years. Treating and assessing physicians and patients were masked to treatment allocation. Results of the primary endpoint, central cerebral volume, have been published elsewhere. Significant differences between the verum and placebo arms were seen in only two measures [normal appearing grey matter (NAGM) p = 0.036 and lesion peak height (PH) p = 0.004], and in both cases there was a greater reduction in MTR in the verum arm. Significant correlations were found of change in MS functional composite with all MTR measures except lesion and normal appearing white matter (NAWM) PH. However, the change in MTR measures over 2 years were small, with only NAGM mean (p = 0.001), lesion peak location (p = 0.11) and mean (p < 0.0001) changing significantly from baseline. These data did not show that lamotrigine was neuroprotective. The clinical correlation of MTR measures was consistent, but the responsiveness to change was limited.

Clinical and imaging correlates of the multiple sclerosis impact scale in secondary progressive multiple sclerosis.

The association of pathology and neurological deficit with quality of life (QoL) in multiple sclerosis (MS) is not fully understood. In this study, magnetic resonance imaging (MRI) measures of pathology--T1 and T2 lesion volume and ratio; active T2 lesion number; global and regional brain volume and atrophy; magnetization transfer ratio (MTR) for lesions, normal appearing grey and white matter (NAGM, NAWM); and spinal cord cross-sectional area-and measures of neurological disability (expanded disability status scale, EDSS), deficit (MS functional composite, MSFC) and inflammatory activity (relapse rate) were compared with the MS impact scale (MSIS-29), in participants in a trial of lamotrigine in secondary progressive MS. Data were collected from 118 people (85 female:33 male) aged 30-61 years (mean 50.6 years)--median EDSS 6.0 (range 4.0-7.5); mean disease duration 20.1 years (range 3-41)--at baseline and 2 years. Regression analysis was used to identify independently significant cross-sectional and longitudinal correlates of the physical (MSIS-phys) and psychological (MSIS-psych) components of the MSIS-29; longitudinal analysis using the 57 people in the placebo arm. The only independently significant correlate of MSIS-phys was 1/timed walk (TW) (p < 0.0001, R (2) = 0.13; p = 0.047, R (2) = 0.09); cross-sectionally the best model for MSIS-psych was the paced auditory serial addition test (PASAT-3) (p = 0.041) and T1-to-T2 lesion volume ratio (p = 0.009) (R (2) = 0.13); longitudinally it was change in 1/TW (p = 0.007), mean NAWM MTR (p = 0.003) and NAGM peak height (p = 0.048) (R (2) = 0.32). These data show that MRI measures and clinical measures do impact on quality of life, but the association is limited.

A longitudinal study of MRI-detected atrophy in secondary progressive multiple sclerosis.

MRI measures of tissue atrophy within the central nervous system may reflect the neurodegenerative process which underpins the progressive phase of multiple sclerosis (MS). There has been limited longitudinal investigation of MRI-detected atrophy in secondary progressive MS. This study includes 56 subjects with secondary progressive MS. Subjects were followed up for 2 years and MRI analysis was conducted at 12 month intervals using the following measures: (1) whole brain (WB) volume change; (2) grey and white matter (WM) volumes; (3) central brain volume; (4) upper cervical spinal cord (SC) area; (5) T2 lesion volumes. Clinical measures included the Expanded Disability Status Scale and the MS Functional Composite. All volumetric MRI measures were assessed for sensitivity, responsiveness, reliability and correlation with disability. The mean annual atrophy rate of WB was 0.59% per year and this was the most responsive atrophy measure assessed. Grey matter (GM) atrophy (-1.18% per year) was greater and more responsive than WM atrophy (0.12% per year). The SC demonstrated the highest atrophy rate at 1.63% per year. WB, GM and SC atrophy all correlated with change in the Multiple Sclerosis Functional Composite z score (r = 0.35, 0.42, 0.34), and GM atrophy was the only correlate of change in the 9 Hole Peg Test and Paced Auditory Serial Addition Test performance. None of the MRI measures correlated with Expanded Disability Status Score progression. Measures of WB, GM and SC atrophy all have attributes for use as surrogate markers in secondary progressive MS trials and improvement in the reliability of the GM and SC volume measurements may enhance these further.

Different white matter lesion characteristics correlate with distinct grey matter abnormalities on magnetic resonance imaging in secondary progressive multiple sclerosis.

BACKGROUND: Although MRI measures of grey matter abnormality correlate with clinical disability in multiple sclerosis, it is uncertain whether grey matter abnormality measured on MRI is entirely due to a primary grey matter process or whether it is partly related to disease in the white matter. METHODS: To explore potential mechanisms of grey matter damage we assessed the relationship of white matter T2 lesion volume, T1 lesion volume, and mean lesion magnetisation transfer ratio (MTR), with MRI measures of tissue atrophy and MTR in the grey matter in 117 subjects with secondary progressive multiple sclerosis. RESULTS: Grey matter fraction and mean grey matter MTR were strongly associated with lesion volumes and lesion MTR mean (r = +/-0.63-0.72). In contrast, only weak to moderate correlations existed between white matter and lesion measures. In a stepwise regression model, T1 lesion volume was the only independent lesion correlate of grey matter fraction and accounted for 52% of the variance. Lesion MTR mean and T2 lesion volume were independent correlates of mean grey matter MTR, accounting for 57% of the variance. CONCLUSIONS: Axonal transection within lesions with secondary degeneration into the grey matter may explain the relationship between T1 lesions and grey matter fraction. A parallel accumulation of demyelinating lesions in white and grey matter may contribute to the association of T2 lesion volume and lesion MTR with grey matter MTR.

Grey matter magnetization transfer ratio independently correlates with neurological deficit in secondary progressive multiple sclerosis.

Although there is substantial brain grey matter pathology in secondary progressive multiple sclerosis (MS), there has been limited investigation of its contribution to disability.This study investigated the correlation of magnetization transfer ratio (MTR) measures taken from brain grey matter, normal appearing white matter (NAWM) and lesions with neurological deficit and disability in 113 people with secondary progressive MS. In order to adjust for the potential effects of focal white matter lesions and global brain atrophy, T2 lesion volume and normalized brain volume (NBV) were also calculated for each subject. Clinical measures included the expanded disability status scale (EDSS) and the multiple sclerosis functional composite (MSFC) scores. Linear regression analysis was used to assess the age- and gender-adjusted correlation of MTR histogram mean, peak height and peak location with the MSFC and individual component measures. Logistic regression analysis was used to determine whether imaging measures could be used to predict if subjects were in the higher disability group (EDSS > or = 6.5).Significant correlations were detected between MSFC composite and mean MTR in (i) normal appearing white matter (NAWM; r = 0.327, p < 0.0001), (ii) grey matter (r = 0.460, p < 0.0001) and (iii) lesions (r = 0.394, p < 0.0001). Although NBV and T2 lesion volume correlated significantly with MSFC, grey matter histogram mean emerged as the best predictor of MSFC score. None of the MRI measures significantly predicted higher EDSS.These results suggest that brain grey matter pathology plays an important role in determining neurological impairment. The apparent paucity of correlation between MRI measures and EDSS is likely to represent the relative insensitivity of the latter measure in this study group.

Magnetic resonance imaging measures of brain and spinal cord atrophy correlate with clinical impairment in secondary progressive multiple sclerosis.

BACKGROUND: Neuroaxonal loss is a pathological substrate of disability in progressive multiple sclerosis (MS) and can be estimated in vivo by measuring tissue atrophy on magnetic resonance imaging (MRI). While there is some evidence that brain atrophy correlates better with disability than T2 lesion load in secondary progressive MS, the clinical relevance of atrophy within specific regions of the central nervous system requires further evaluation. METHODS: Clinical and MRI examinations were performed in 117 subjects with secondary progressive MS. MRI analysis included measures of normalized brain volume (NBV), normalized grey matter (NGMV) and white matter volume (NWMV), central cerebral volume (CCV), spinal cord cross-sectional area (SCCA), and brain T2 and T1 lesion volume. Clinical assessments included the expanded disability status scale (EDSS) and MS functional composite (MSFC). RESULTS: All MRI measures correlated significantly with the MSFC score, with the strongest correlation being for the NBV (r = 0.47; P < 0.001). NBV and SCCA were the only significant independent predictors of the MSFC score in a stepwise regression model containing all the MRI measures, and SCCA was the only MRI measure to show a significant association with the EDSS. While NGMV had stronger correlations with the clinical variables than NWMV, NBV was more correlated with clinical impairment than either measure. CONCLUSIONS: This data suggests that measures of atrophy, particularly of the whole brain and spinal cord, are relevant and useful disease markers in secondary progressive MS.

The origin and development of retinal astrocytes in the mouse.

Astrocytes, a class of glia which appear in the mammalian retina late in development, have been postulated either to originate in situ from Müller cells or extra-retinally from the optic stalk epithelium, only subsequently invading the eye. The site of origin and the developmental characteristics of retinal astrocytes were examined in the mouse, a species not previously studied for this purpose. Sections of normal eyes and stalks at different ages were examined. Cells positive for glial fibrillary acidic protein (GFAP) were first observed at post-conceptional day 17 at the optic disc end of the stalk. From this site, the GFAP-positive cells migrated into and across the retina at a rate of approximately 290 microns per day, reaching its edge by post-conceptional day 28. While migrating across the retina, the astrocytes progressively increased in size and morphological complexity, observations confirmed by measurement of their fractal dimension. Over the same period, a wave of differentiation swept along the stalk in the cranial direction. Further evidence that retinal astrocytes are born outside the retina emerged when foetal hemiretinae with or without optic stalks were explanted to the chorioallantoic membrane of the chick. When examined one to twelve days later, no explant cultured without the optic stalk contained GFAP-positive astrocytes, while explants with the stalk left attached contained relatively normal numbers of astrocytes. We observed, using fluorescence confocal microscopy, that retinal astrocytes in the mouse as in the rat, associate predominantly with blood vessels, not axonal bundles. It was of interest to determine whether this class of glia is essential to the normal cytoarchitectural development of the neural retina. Morphological analysis of the explants revealed no observable differences in cytoarchitecture or in the timing of developmental events between retinae maturing with or without astrocytes. It was therefore concluded that astrocytes may not be essential to the normal structural development of the murine retina.

Tetratological evaluation of mouse fetuses after paternal alcohol ingestion.

Numerous studies have appeared in the literature which suggest that paternal alcohol consumption may have adverse effects on subsequent offspring. However, to date, no teratologic examination has been performed on fetuses conceived subsequent to paternal alcohol consumption. The present study has examined fetuses conceived by alcohol-treated male Swiss webster mice for gross anatomical congenital defects in an attempt to evaluate a possible mechanism for decreased viability of offspring sired by alcoholic males. Sexually mature males were maintained for 28 days on a total liquid nutriment diet in which alcohol (6.3%, v/v, U.S.P. ethanol) comprised 32% of the caloric content. Subsequently, the animals were mated with nulliparous females. On day 18 of gestation, the gravid females were sacrificed and the fetuses were examined for congenital defects. Only 14% of the matings which occurred 3--5 days after alcohol treatment resulted in pregnancy, as compared to a pregnancy rate of 100% for matings from pair-fed controls during the same period. Fetuses sired by alcohol-treated males during this time had reduced birth weights (0.85 +/- 0.04 g vs 0.92 +/- 0.11 g;p = 0.059) and crown-rump lengths (1.83 +/- 0.06 cm vs 1.99 +/- 0.11 cm;p less than 0.001) as compared to control fetuses. The frequency of congenital defects did not differ significantly between the experimental and control groups. No significant differences were noted between experimental and control progeny conceived more than 5 days after alcohol treatment. These results suggest that although some changes may be seen in progeny sired by alcohol treated males, the specific anomalies associated with the Fetal Alcohol Syndrome are most probably not due to paternal alcoholism.

Autoantibodies to retinal astrocytes associated with age-related macular degeneration.

Sera from 128 patients with age-related macular degeneration (AMD) were examined and profiles of a variety of serum constituents, including immunoglobulins, alpha and beta globulins and autoantibodies, were tabulated. A similar series of tests were carried out on 20 control sera. The results indicate a higher incidence of serum abnormalities, particularly involving alpha-2 globulin, in patients with disturbance of pigmentation of the retinal pigment epithelium (RPE). The sera were further tested for the presence of autoantibodies with specificity for retinal tissue, and five major staining patterns were observed. Many sera produced patterns of labelling on human retina identical to that observed using labelled monoclonal anti-glial fibrillary acid protein (GFAP) antibodies, which are an established marker of retinal astrocytes. Although anti-retinal autoantibodies have been reported in association with a number of ocular pathologies, the observation of anti-astrocyte autoantibodies is new. Astrocytes are involved in the maintenance of the blood-retinal barrier (BRB) and also appear to be the facultative antigen-presenting cells of neural tissue. The present results indicate that the formation of anti-astrocyte autoantibodies may be an early feature of the pathogenesis of AMD.