Decreased brain reward produced by ethanol withdrawal.

Abstinence from chronic administration of various drugs of abuse such as ethanol, opiates, and psychostimulants results in withdrawal syndromes largely unique to each drug class. However, one symptom that appears common to these withdrawal syndromes in humans is a negative affective/motivational state. Prior work in rodents has shown that elevations in intracranial self-stimulation (ICSS) reward thresholds provide a quantitative index that serves as a model for the negative affective state during withdrawal from psychostimulants and opiates. The current study sought to determine whether ICSS threshold elevations also accompany abstinence from chronic ethanol exposure sufficient to induce physical dependence. Rats prepared with stimulating electrodes in the lateral hypothalamus were trained in a discrete-trial current-intensity ICSS threshold procedure; subsequently they were subjected to chronic ethanol administration in ethanol vapor chambers (average blood alcohol level of 197 mg/dl). A time-dependent elevation in ICSS thresholds was observed following removal from the ethanol, but not the control, chambers. Thresholds were significantly elevated for 48 hr after cessation of ethanol exposure, with peak elevations observed at 6-8 hr. Blood alcohol levels were directly correlated with the magnitude of peak threshold elevation. Ratings of traditional overt signs of withdrawal showed a similar time course of expression and resolution. The results suggest that decreased function of reward systems (elevations in reward thresholds) is a common element of withdrawal from chronic administration of several diverse classes of abused drugs.

Localization of specific erythropoietin binding sites in defined areas of the mouse brain.

The main physiological regulator of erythropoiesis is the hematopoietic growth factor erythropoietin (EPO), which is induced in response to hypoxia. Binding of EPO to the EPO receptor (EPO-R), a member of the cytokine receptor superfamily, controls the terminal maturation of red blood cells. So far, EPO has been reported to act mainly on erythroid precursor cells. However, we have detected mRNA encoding both EPO and EPO-R in mouse brain by reverse transcription-PCR. Exposure to 0.1% carbon monoxide, a procedure that causes functional anemia, resulted in a 20-fold increase of EPO mRNA in mouse brain as quantified by competitive reverse transcription-PCR, whereas the EPO-R mRNA level was not influenced by hypoxia. Binding studies on mouse brain sections revealed defined binding sites for radioiodinated EPO in distinct brain areas. The specificity of EPO binding was assessed by homologous competition with an excess of unlabeled EPO and by using two monoclonal antibodies against human EPO, one inhibitory and the other noninhibitory for binding of EPO to EPO-R. Major EPO binding sites were observed in the hippocampus, capsula interna, cortex, and midbrain areas. Functional expression of the EPO-R and hypoxic upregulation of EPO suggest a role of EPO in the brain.

Species specificity in the cell-free conversion of prion protein to protease-resistant forms: a model for the scrapie species barrier.

Scrapie is a transmissible neurodegenerative disease that appears to result from an accumulation in the brain of an abnormal protease-resistant isoform of prion protein (PrP) called PrPsc. Conversion of the normal, protease-sensitive form of PrP (PrPc) to protease-resistant forms like PrPsc has been demonstrated in a cell-free reaction composed largely of hamster PrPc and PrPsc. We now report studies of the species specificity of this cell-free reaction using mouse, hamster, and chimeric PrP molecules. Combinations of hamster PrPc with hamster PrPsc and mouse PrPc with mouse PrPsc resulted in the conversion of PrPc to protease-resistant forms. Protease-resistant PrP species were also generated in the nonhomologous reaction of hamster PrPc with mouse PrPsc, but little conversion was observed in the reciprocal reaction. Glycosylation of the PrPc precursors was not required for species specificity in the conversion reaction. The relative conversion efficiencies correlated with the relative transmissibilities of these strains of scrapie between mice and hamsters. Conversion experiments performed with chimeric mouse/hamster PrPc precursors indicated that differences between PrPc and PrPsc at residues 139, 155, and 170 affected the conversion efficiency and the size of the resultant protease-resistant PrP species. We conclude that there is species specificity in the cell-free interactions that lead to the conversion of PrPc to protease-resistant forms. This specificity may be the molecular basis for the barriers to interspecies transmission of scrapie and other transmissible spongiform encephalopathies in vivo.

Cosegregation analysis of natriuretic peptide genes and blood pressure in the spontaneously hypertensive rat

1. The natriuretic peptide precursor A (Nppa) and B (Nppb) genes are candidate genes for hypertension and cardiac hypertrophy in the spontaneously hypertensive rat (SHR). The purpose of the present study was to determine the role of the Nppa and Nppb genes in the development of hypertension in the SHR. 2. A cohort (n = 162) of F2 segregating intercross animals was established between strains of hypertensive SHR and normotensive Wistar-Kyoto rats. Blood pressure and heart weight were measured in each rat at 12-16 weeks of age. Rats were genotyped using 11 informative microsatellite markers, distributed in the vicinity of the Nppa marker on rat chromosome 5 including an Nppb marker. The phenotype values were compared with genotype using the computer package MAP-MAKER 3.0 (Whitehead Institute, Boston, MA, USA) to determine whether there was a link between the genetic variants of the natriuretic peptide family and blood pressure or cardiac hypertrophy. 3. A strong correlation was observed between the Nppa marker and blood pressure. A quantitative trait locus (QTL) for blood pressure on chromosome 5 was identified between the Nppa locus and the D5Mgh15 marker, less than 2 cM from the Nppa locus. The linkage score for the blood pressure QTL on chromosome 5 was 3.8 and the QTL accounted for 43% of the total variance of systolic blood pressure, 54% of diastolic blood pressure and 59% of mean blood pressure. No association was found between the Nppb gene and blood pressure. This is the first report of linkage between the Nppa marker and blood pressure in the rat. There was no correlation between the Nppa or Nppb genes or other markers in this region and either heart weight or left ventricular weight in F2 rats. 4. These findings suggest the existence of a blood pressure-dependent Nppa marker variant or a gene close to Nppa predisposing to spontaneous hypertension in the rat. It provides a strong foundation for further detailed genetic studies in congenic strains, which may help to narrow down the location of this gene and lead to positional cloning.

An Internet training intervention for people with traumatic brain injury: Barriers and outcomes

Primary objective: To test whether people with cognitive-linguistic impairments following traumatic brain injury could learn to use the Internet using specialized training materials. Research design: Pre-post test design. Methods and procedures: Seven participants were each matched with a volunteer tutor. Basic Internet skills were taught over six lessons using a tutor's manual and a student manual. Instructions used simple text and graphics based on Microsoft Internet Explorer 5.5. Students underwent Internet skills assessments and interviews pre- and post-training. Tutors completed a post-training questionnaire. Main outcomes and results: Six of seven participants reached moderate-to-high degrees of independence. Literacy impairment was an expected training barrier; however, cognitive impairments affecting concentration, memory and motivation were more significant. Conclusions: Findings suggest that people with cognitive-linguistic impairments can learn Internet skills using specialized training materials. Participants and their carers also reported positive outcomes beyond the acquisition of Internet skills.

Parasitic isopods (Gnathia sp.) reduce haematocrit in captive blackeye thicklip (Labridae) on the Great Barrier Reef

Captive Hemigymnus melapterus exposed to large numbers of cultured juvenile parasitic isopods (Gnathia sp.) had significantly lower haematocrit (median 27-62% +/- 5-83% inter-quartile range) than uninfected, control fish (median 32-73% +/- 4-90%). This study is the first to show that juvenile Gnathia sp. reduce total blood volume in H. melapterus. The low haematocrit in infected fish was most likely due to plasma replacing erythrocytes lost as a result of isopods feeding on fish blood. (c) 2005 The Fisheries Society of the British Isles.

Tolerance of endolithic algae to elevated temperature and light in the coral Montipora monasteriata from the southern Great Barrier Reef

Photosynthetic endolithic algae and cyanobacteria live within the skeletons of many scleractinians. Under normal conditions, less than 5% of the photosynthetically active radiation (PAR) reaches the green endolithic algae because of the absorbance of light by the endosymbiotic dinoflagellates and the carbonate skeleton. When corals bleach (loose dinoflagellate symbionts), however, the tissue of the corals become highly transparent and photosynthetic microendoliths may be exposed to high levels of both thermal and solar stress. This study explores the consequence of these combined stresses on the phototrophic endoliths inhabiting the skeleton of Montipora monasteriata, growing at Heron Island, on the southern Great Barrier Reef. Endoliths that were exposed to sun after tissue removal were by far more susceptible to thermal photoinhibition and photo-damage than endoliths under coral tissue that contained high concentrations of brown dinoflagellate symbionts. While temperature or light alone did not result in decreased photosynthetic efficiency of the endoliths, combined thermal and solar stress caused a major decrease and delayed recovery. Endoliths protected under intact tissue recovered rapidly and photoacclimated soon after exposure to elevated sea temperatures. Endoliths under naturally occurring bleached tissue of M. monasteriata colonies (bleaching event in March 2004 at Heron Island) acclimated to increased irradiance as the brown symbionts disappeared. We suggest that two major factors determine the outcome of thermal bleaching to the endolith community. The first is the microhabitat and light levels under which a coral grows, and the second is the susceptibility of the coral-dinoflagellates symbiosis to thermal stress. More resistant corals may take longer to bleach allowing endoliths time to acclimate to a new light environment. This in turn may have implications for coral survival.

The use of hypertonic saline for treating intracranial hypertension after traumatic brain injury

The past decade has witnessed a resurgence of interest in the use of hypertonic saline for low-volume resuscitation after trauma. Preliminary studies suggested that benefits are limited to a subgroup of trauma patients with brain injury, but a recent study of prehospital administration of hypertonic saline to patients with traumatic brain injury failed to confirm a benefit. Animal and human studies have demonstrated that hypertonic saline has clinically desirable physiological effects on cerebral blood flow, intracranial pressure, and inflammatory responses in models of neurotrauma. There are few clinical studies in traumatic brain injury with patient survival as an end point. In this review, we examined the experimental and clinical knowledge of hypertonic saline as an osmotherapeutic agent in neurotrauma.

Brain activity during automatic semantic priming revealed by event-related functional magnetic resonance imaging

Semantic priming occurs when a subject is faster in recognising a target word when it is preceded by a related word compared to an unrelated word. The effect is attributed to automatic or controlled processing mechanisms elicited by short or long interstimulus intervals (ISIs) between primes and targets. We employed event-related functional magnetic resonance imaging (fMRI) to investigate blood oxygen level dependent (BOLD) responses associated with automatic semantic priming using an experimental design identical to that used in standard behavioural priming tasks. Prime-target semantic strength was manipulated by using lexical ambiguity primes (e.g., bank) and target words related to dominant or subordinate meaning of the ambiguity. Subjects made speeded lexical decisions (word/nonword) on dominant related, subordinate related, and unrelated word pairs presented randomly with a short ISI. The major finding was a pattern of reduced activity in middle temporal and inferior prefrontal regions for dominant versus unrelated and subordinate versus unrelated comparisons, respectively. These findings are consistent with both a dual process model of semantic priming and recent repetition priming data that suggest that reductions in BOLD responses represent neural priming associated with automatic semantic activation and implicate the left middle temporal cortex and inferior prefrontal cortex in more automatic aspects of semantic processing.

Quantitative microscopic analysis of histological sections of brain tissue

This article reviews methods for quantifying the abundance of histological features in thin tissue sections of brain such as neurons, glia, blood vessels, and pathological lesions. The sampling methods by which quantitative measures can be obtained are described. In addition, methods are described for determining the spatial pattern of an object and for measuring the degree of spatial correlation between two or more histological features.

Spatial correlations between the vacuolation, prion protein (PrPsc) deposits and the cerebral blood vessels in sporadic Creutzfeldt-Jakob disease

In the variant form of Creutzfeldt-Jakob disease (vCJD), 'florid' deposits of the protease resistant form of prion protein (PrP(sc)) were aggregated around the cerebral blood vessels suggesting the possibility that prions may spread into the brain via the cerebral microcirculation. The objective of the present study was to determine whether the pathology was spatially related to blood vessels in cases of sporadic CJD (sCJD), a disease without an iatrogenic etiology, and therefore, less likely to be caused by hematogenous spread. Hence, the spatial correlations between the vacuolation ('spongiform change'), PrP(sc) deposits, and the blood vessels were studied in immunolabelled sections of the cerebral cortex and cerebellum in eleven cases of the common M/M1 subtype of sCJD. Both the vacuolation and the PrP(sc) deposits were spatially correlated with the blood vessels; the PrP(sc) deposits being more focally distributed around the vessels than the vacuoles. The frequency of positive spatial correlations was similar in the different gyri of the cerebral cortex, in the upper and lower cortical laminae, and in the molecular layer of the cerebellum. It is hypothesized that the spatial correlation is attributable to factors associated with the blood vessels which promote the aggregation of PrP(sc) to form deposits rather than representing the hematogenous spread of the disease. The aggregated form of PrP(sc) then enhances cell death and may encourages the development of vacuolation in the vicinity of the blood vessels.

Methods of studying the planar distribution of objects in histological sections of brain tissue

This article reviews the statistical methods that have been used to study the planar distribution, and especially clustering, of objects in histological sections of brain tissue. The objective of these studies is usually quantitative description, comparison between patients or correlation between histological features. Objects of interest such as neurones, glial cells, blood vessels or pathological features such as protein deposits appear as sectional profiles in a two-dimensional section. These objects may not be randomly distributed within the section but exhibit a spatial pattern, a departure from randomness either towards regularity or clustering. The methods described include simple tests of whether the planar distribution of a histological feature departs significantly from randomness using randomized points, lines or sample fields and more complex methods that employ grids or transects of contiguous fields, and which can detect the intensity of aggregation and the sizes, distribution and spacing of clusters. The usefulness of these methods in understanding the pathogenesis of neurodegenerative diseases such as Alzheimer's disease and Creutzfeldt-Jakob disease is discussed. © 2006 The Royal Microscopical Society.

Classic beta-amyloid deposits cluster around large diameter blood vessels rather than capillaries in sporadic Alzheimer's disease

Various hypotheses could explain the relationship between beta-amyloid (Abeta) deposition and the vasculature in Alzheimer's disease (AD). Amyloid deposition may reduce capillary density, affect endothelial cells of blood vessels, result in diffusion from blood vessels, or interfere with the perivascular clearance mechanism. Hence, the spatial pattern of the classic ('cored') type of Abeta deposit was studied in the upper laminae (I,II/III) of the superior frontal gyrus in nine cases of sporadic AD (SAD). Sections were immunostained with antibodies against Abeta and with collagen IV to study the relationships between the spatial distribution of the classic deposits and the blood vessel profiles. Both the classic deposits and blood vessel profiles were distributed in clusters. In all cases, there was a positive spatial correlation between the clusters of the classic deposits and the larger diameter (>10 microm) blood vessel profiles and especially the vertically penetrating arterioles. In only 1 case, was there a significant spatial correlation between the clusters of the classic deposits and the smaller diameter (<10 microm) capillaries. There were no negative correlations between the density of Abeta deposits and the smaller diameter capillaries. In 9/11 cases, the clusters of the classic deposits were significantly larger than those of the clusters of the larger blood vessel profiles. In addition, the density of the classic deposits declined as a negative exponential function with distance from a vertically penetrating arteriole. These results suggest that the classic Abeta deposits cluster around the larger blood vessels in the upper laminae of the frontal cortex. This aggregation could result from diffusion of proteins from blood vessels or from overloading the system of perivascular clearance from the brain.

Measuring the degree of spatial correlation between histological features in thin sections of brain tissue

Histological features visible in thin sections of brain tissue, such as neuronal perikarya, blood vessels, or pathological lesions may exhibit a degree of spatial association or correlation. In neurodegenerative disorders such as AD, Pick's disease, and CJD, information on whether different types of pathological lesion are spatially correlated may be useful in elucidating disease pathogenesis. In the present article the statistical methods available for studying spatial association in histological sections are reviewed. These include tests of interspecific association between two or more histological features using χ2 contingency tables, measurement of 'complete' and 'absolute' association, and more complex methods that use grids of contiguous samples. In addition, the use of correlation matrices and stepwise multiple regression methods are described. The advantages and limitations of each method are reviewed and possible future developments discussed.

Florid prion protein (PrP) plaques in patients with variant Creutzfeldt-Jakob disease (vCJD) are spatially related to blood vessels

This study tested the hypothesis that variations in the density of the florid prion protein (PrP) plaques in the brain of patients with variant Creutzfeldt-Jakob disease (vCJD) were spatially related to blood vessels. In 81% of areas of the cerebral cortex sampled and in 37% of the remaining areas, which included the hippocampus, dentate gyrus, and cerebellum, there was a positive spatial correlation between the density of the florid plaques and the larger blood vessel profiles. The frequency of the positive spatial correlations was similar in different anatomical areas of the cerebral cortex and in the upper compared with the lower cortical laminae. The data support the hypothesis that the florid plaques cluster around the larger blood vessels in vCJD, the density of associated plaques increasing with vessel size. The development of florid plaques close to blood vessels may be due to factors associated with the blood vessels that enhance the aggregation of PrP to form the dense cores of florid plaques and is unlikely to reflect the haematogenous spread of PrP into the brain.