No description available.

No description available.

La sclérose latérale amyotrophique [SLA] est une pathologie idiopathique à issue fatale caractérisée par la dégénérescence progressive et sélective des motoneurones du système nerveux central et périphérique. La SLA n’est pas exclusivement identifiée comme une maladie de la voie pyramidale, mais considérée plus largement comme une pathologie neurodégénérative multisystème. L’étude des mécanismes posturaux dans cette population n’a pas fait l’objet d’une grande attention. Dans ce travail de thèse, une exploration en imagerie cérébrale multimodale (imagerie en tenseur de diffusion [DTI] et morphométrie basée sur le voxel [VBM]) est proposée chez des patients SLA avec instabilité posturale [AIP] et stables [SIP] en vue de vérifier l’intégrité morphologique et structurelle des régions corticales et sous-corticales posturales. La comparaison entre les sujets contrôles et les patients SLA a démontré une augmentation significative du volume de la substance grise au niveau du noyau caudé chez les patients stables (SIP vs contrôle p<0,001 ; SIP vs AIP p<0,01). L’évaluation structurelle a révélé une diminution de la fraction d’anisotropie [FA] au niveau de l’aire motrice supplémentaire [AMS] dans les deux groupes de patients par rapport aux contrôles (contrôle vs SIP p<0,05 ; contrôle vs AIP p<0,001). Au niveau du noyau caudé, le groupe AIP a présenté une diminution de la valeur de la FA par rapport aux sujets contrôles (p<0,001) et aux sujets SIP (p<0,05). Ainsi, ces résultats contribuent à une meilleure caractérisation et compréhension des atteintes corticales et sous corticales des régions qui interviennent dans la posture chez les patients SLA. / The Amyotrophic Lateral Sclerosis [ALS] is an idiopathic pathology with a fatal outcome. It is characterized by a progressive and selective degeneration of motor neurons in the central and peripheral nervous system. ALS is no longer exclusively identified as a disease of the pyramidal pathway, but it is considered more broadly as multisystem neurodegenerative pathology. However, the analysis of postural processes in these patients has not been well studied in the literature. Multimodal brain imaging (Diffusion Tensor Imaging [DTI] and Voxel Based Morphometry [VBM]) exploration was performed for ALS patients with postural instability [AIP] and without postural instability [SIP] to test the morphometric and structural integrity of postural cortical and subcortical regions. A significant increase of gray matter in caudate nucleus volume has been noticed for stable patients (SIP vs controls p<0.001, SIP vs AIP p<0.01). The structural evaluation revealed a decrease of the Fractional Anisotropy [FA] at the Supplementary Motor Area [SMA] level in both groups of patients compared to controls (controls vs SIP p<0.05, controls vs. AIP p<0.001). At the caudate nucleus, the AIP group showed FA value decrease compared to controls (p<0.001) and SIP subjects (p<0.05). Thus, these results would contribute to a better characterization and understanding of the cortical and subcortical impairments of the postural regions in ALS patients.

Declines in amphibian populations have prompted study of their ecology and distribution. The purpose of this study was to survey two sites located within different physiographic and one herpetofaunal region of Northeast Tennessee, comparing species composition and activity. The first, Henderson Wetland, is in the Appalachian Ridge and Valley physiographic region. The second, John's Bog, is in the Blue Ridge. Survey methods included random walks, aural surveys, and point source collections during a 16-month period (February 1999 to May 2000). Nine caudate (Plethodontidae) and one anuran species (Ranidae) were found in John's Bog. Seven caudate (Ambystomatidae, Plethodontidae, Salamandridae) and five anuran species (Hylidae, Ranidae) were found in Henderson Wetland. Assemblages were compared using an index of community similarity. Sites differed regarding amphibians detected. Temporal activity was not compared because of different species compositions. Instead, temporal data were compared to literature. Data will be used in future amphibian studies and site management.

Vocal plasticity is presumed to be a key element underlying the evolution of human speech and language, but the mechanisms and neuroanatomical basis for this plasticity remain largely unknown. The Mexican free-tailed bat, Tadarida brasiliensis, presents a unique opportunity to advance our understanding of the evolution and neurobiology of mammalian vocal communication because this animal displays elements of vocal complexity and plasticity that are more sophisticated than any mammal other than humans, including non-human primates. Current models of vocal control in mammals do not account for the vocal complexity of free-tailed bats. The purpose of this dissertation is to fill that gap in knowledge by identifying a possible neuronal basis for vocal complexity in free-tailed bats. This will be achieved by 1) providing a detailed analysis of the free-tailed bat’s vocal behaviors, 2) mapping the distribution of neurotransmitter receptor types suspected of involvement in vocal control, 3) identifying brain regions that exhibit increased neuronal activity during vocalizing, and 4) pharmacologically manipulating putative vocal control regions to confirm and characterize their function in vocalizing. Analysis of Tadarida’s vocal behavior indicated that they have a vast vocal repertoire, including many different call types, context-dependent sensory-feedback driven vocal plasticity, and syntactically-organized stereotyped songs. Their vocal behavior changed seasonally, so I mapped the distribution of melatonin binding sites in the brain, finding high densities in the striatum, similar to dopamine receptor distribution. I then used immunohistochemical labeling of the immediate early gene cfos to map neuronal activation in brains of highly vocal bats to find ROIs activated by vocal production. This technique not only identified all previously known regions of the mammalian vocal motor pathway but also revealed activity in novel brain regions that could potentially account for vocal plasticity, including a localized region of the basal ganglia, the dorsolateral caudate nucleus, and the anterior cingulate region of the frontal cortex. Pharmacological excitation of these regions evoked complex vocal sequences similar to the songs recorded in the field and lab. These results support the hypothesis that the mammalian basal ganglia may play a crucial role in the plasticity and complexity of mammalian vocal behaviors.

To characterize corticostriatal projections from rodent sensorimotor cortex, the anterograde tracers biotinylated dextran amine (BDA) and fluororuby (FR) were injected into the whisker representations of the primary motor (MI) and somatosensory (SI) cortices. Reconstructions of labeled terminals and their beaded varicosities in the neostriatum and thalamus were analyzed quantitatively to determine the degree of labeled overlap in both of these subcortical structures. Corticostriatal projections from the vibrissal representation in MI were more extensive than corresponding projections from SI. Both cortical areas sent dense projections to the dorsolateral neostriatum, but the MI vibrissal representation also projected to regions located more rostrally and medially. Despite these differences, both MI and SI projected to overlapping parts of the dorsolateral neostriatum. Tracer injections in both cortical areas also produced dense anterograde and retrograde labeling in the medial sector of the posterior complex of the thalamus (POm). Because POm is somatotopically organized and has reciprocal connections with both SI and MI cortices, the amount of labeled overlap in POm was used to indicate whether the tracers were injected into corresponding whisker representations of MI and SI. We found that the proportion of labeled overlap in the neostriatum was highly correlated with the amount of labeled overlap in POm. These results indicate that the rodent neostriatum receives convergent projections from corresponding regions in MI and SI cortex. Furthermore, the thalamocortical projections of the POm indicate that it may modulate corticostriatal outputs from corresponding representations in MI and SI.

Salamanders are one of the most at-risk taxa in the world due to habitat destruction, pollution, climate change, invasive diseases, and more. This has led to a need for conservation breeding programs that are often associated with zoos and aquaria. Salamanders can be difficult to breed in captivity, though, due to their dependence on specific environmental cues and other unknown factors that stimulate sperm and egg production. To overcome these challenges, assisted reproductive technologies (ART) such as exogenous hormone administration, sperm cryopreservation, and in-vitro fertilization have been developed to increase offspring propagation and maintain genetic diversity. If genetically robust populations of salamander species can be sustainably managed ex situ into the future, then their species can be protected in situ through practices such as reintroductions into native habitats. Given the importance of salamanders to healthy, functioning ecosystems, my doctoral research focused on methods to advance caudate conservation efforts through ART. This dissertation addresses four key areas targeting salamander reproduction for conservation: 1) Novel, non-invasive hormone administration routes; 2) Sperm extender toxicity; 3) Novel sperm cryoprotectants; and 4) Application of ART to target salamander species. The objectives were to: 1) Compare nasal, oral, and intramuscular delivery routes of gonadotropin-releasing hormone on spermic response; 2) Compare sperm extenders at varying osmolalities for maintaining sperm quality over time; 3) Test dimethyl sulfoxide versus dimethylformamide as cryoprotectants to increase frozen-thawed sperm viability, motility, and fertilization capability in the eastern tiger salamander (Ambystoma tigrinum); and 4) Transfer ART protocols developed from the eastern tiger salamander to the eastern hellbender (Cryptobranchus alleganiensis) and spotted salamander (Ambystoma maculatum). This work answers critical questions that should help advance salamander ART research into the future and lead to more sustainably managed caudate populations.

No description available.

Cognitive deficits in first-episode psychosis (FEP) are well documented including deficits in cognitive control, but how sex may influence or impact these cognitive deficits is not well known. Cognitive deficits may impact multiple neural networks, including the fronto-parietal network (FPN). How sex may influence the structural integrity of regions in the FPN is also an important area of research in FEP that may provide further insight into the beginnings of the disease. The current study aimed to examine sexual dimorphisms in structural integrity of the frontoparietal network (FPN) and its role in cognitive control in FEP. A total of 111 FEP patients (68 male, 43 female) and 55 healthy control participants (35 male, 20 female) from the Human Connectome Project for Early Psychosis who underwent T1-weighted magnetic resonance imaging and neuropsychological testing were included in the study. Regions of interest (ROIs) included: left and right superior frontal gyrus, left and right middle frontal gyrus, left inferior frontal gyrus, left and right inferior parietal gyrus, right caudate and left thalamus. Using high-dimensional brain mapping procedures, surface shape of the right caudate and left thalamus was characterized using Large Deformation Diffeomorphic Metric Mapping, and cortical thickness of frontal and parietal regions was estimated using the FreeSurfer toolkit. Cognitive control was assessed using the Fluid Cognition Composite score from the NIH Toolbox Cognition Battery. Multivariate ANOVA models tested group differences, separated by sex, in cortical thickness ROIs, in addition to a whole-brain vertex-wise analysis. Vertex-wise statistical surface t-maps evaluated differences in subcortical surface shape, and Pearson correlations tested relationships between brain regions and Fluid Cognition performance. Results of deep brain region comparisons between schizophrenia males (SCZM) and schizophrenia females (SCZF) groups revealed significant outward deformation at the tail of the right caudate and significant inward deformation along the dorsal aspects of the right caudate. Additionally, significant inward deformation in multiple nuclei of the left thalamus were revealed. Significant negative relationships between Fluid Cognition and the left superior/middle frontal gyrus (r = -0.24, p = 0.05) in the male FEP group were observed. Additionally, significant positive relationships between Fluid Cognition and left inferior frontal gyrus (r = 0.35, p = 0.02) and left inferior parietal gyrus (r = 0.35, p = 0.02) in the female FEP group were found. Support vector machine models were trained using measures of cortical thickness and subcortical shape deformation values in all cohorts to classify participants based on diagnosis. Classification accuracy in all testing models ranged from 75-81%. Overall, findings revealed significant differences of subcortical structures, including smaller caudal and thalamic volume, in male FEP compared to female FEP, providing evidence of the importance to examine sex differences at the first episode. Increased consideration for the role of deep-brain structures in male and female FEP can aid in the clinical characterization of the early stages of the disease.

Membrane bound AChE from calf brain caudate nucleus was solubilized by use of ion-free media in presence of 10~ M EDTA and 10“5M tetracaine. The irreversible release of AChE was more effectively inhibited by divalent ions compared to monovalent ions added to the medium. EDTA appears to chelate divalent ions released from the tissue while tetracaine competes with the same ions at the membrane. The tetracaine effect is restricted to the procaine series of local anesthetics. Small amounts of soluble AChE are present in the cytosol fraction. In fresh preparations most of the enzyme appeared in a form having a molecular weight of 80.000 daltons as determined by gel filtration. The enzyme seems to be released in this form. It is proposed that this form represents the monomer form of the enzyme. In solution the AChE aggregates seemingly together with a factor that is released from the membrane in amounts stafchio- metric to the enzyme. By treatment with DEAE-Sephadex the enzyme preparation can be made non-aggregating. A highly purified nonaggregating monomeric AChE Specific activity 17150 micromoles acetylthiocholine hydrolyzed per minute at 27° C per mg protein) was obtained by affinity chromatography. Some anomalous binding phenomena was observed during the affinity chromatographic purification. The main observation was that edrophonium eluted crude enzyme preparation adsorbed to the affinity gel in a biphasic manner. It was found that in the crude preparation there is present besides unspecific material competing with the enzyme for the affinity gels a factor that increases the affinity of AChE to certain cholinergic ligands. Since the enzyme could be titrated by the factor it seems to have a very high affinity to the enzyme and the biphasic elution curve is explained by the presence of free as well as factor- bound enzyme in the preparation. In search for compounds having a similar effect it was found that fluoride ion too increased the affinity of AChE to the same ligands as the factor. The affinity of edrophonium to the site defined by the binding of AChE to MTA-CH (65x10“5m) is lower than that defined by the enzyme inhibitory constant (1.8xlO“7M). As an explanation of this finding it is proposed that the substrate induces a conformation having high affinity to edrophonium, a conformation that has a comparatively low relaxation rate. Thus acetylcholinesterase may be added to the list of enzymes that have hystere- tic properties. / <p>S. 1-54: sammanfattning, s. 55-100: 4 uppsatser</p> / digitalisering@umu