Jens Chr. Sørensen

Chronic subthalamic high-frequency deep brain stimulation in Parkinson's disease – a histopathological study

This study describes the pathological findings in the brain of a patient with Parkinsons disease (PD) treated with bilateral subthalamic high‐frequency deep brain stimulation (STN DBS) for 29 months prior to death. After routine neuropathological examination, tissue blocks containing the electrode tracts, the subthalamic nucleus (STN), the substantia nigra and the pre‐frontal cortex were paraffin embedded and cut into 5‐μm‐thick serial sections and stained with several conventional staining methods and immunohistochemistry. Bilateral nigral depigmentation, cell loss and Lewy body formation confirmed the diagnosis of PD. Microscopic evaluation furthermore confirmed the location of the electrodes in the STN. The electrode tracts were surrounded by a 150‐μm‐wide glial fibrillary acidic protein (GFAP)‐positive capsule consisting of a thin collagen layer lining the lumen of the tract, whilst an area with few cells and axons constituted the capsule wall towards the surrounding normal brain tissue. The brain tissue appeared normal outside the capsule boundaries with no difference in areas of stimulation compared with areas of no stimulation. Our results correspond with previous studies performed after fewer months of STN DBS and indicate mild histopathological changes in the vicinity of the electrode tract, appearing to result from the electrode placement and not from the electrical stimulation.

A MRI-compatible stereotaxic localizer box enables high-precision stereotaxic procedures in pigs.

We present a nonmagnetic Plexiglas stereotaxic localizer box that can be fitted directly to the pig skull by aluminum screws, allowing stereotaxic MRI or ventriculography and subsequent high-precision stereotaxic procedures. The localizer box was used to target the subthalamic nucleus (STN) bilaterally in five female Göttingen minipigs. Stereotaxic markers were inserted in the pig skull, the head fixated in the localizer box by aluminum screws inserted bilaterally in the zygoma bone with the hard palate locked on a horizontal palate holder. MRI was obtained on a 3T-MR-imager revealing the relation between the inserted markers and the estimated STN-position, and thus the target coordinates. After the MRI, a stereotaxic frame with attached micromanipulator was locked on to the localizer box converting it into a stereotaxic device. The stereotaxic markers were exposed and used as starting point for the stereotaxic procedure, whereby a microelectrode for electrolytic lesioning was inserted in the STN. Postmortem histological analysis revealed 70% correct STN-targeting. The average distance from the lesion center to the STN center was 1.2 mm with a S.D. of 1.1 mm. The most displaced lesion being 3.6 mm from the STN center. We conclude that the described localizer box secure firm head fixation, allowing stereotaxic MRI and subsequent conversion into a stereotaxic device for high-precision stereotaxic procedures.

Fluoro-Gold tracing of zinc-containing afferent connections in the mouse visual cortices

SummaryTo identify zinc-containing projections to the visual areas, we injected Fluoro-Gold into the occipital cortex of the mouse. Five days later, the mice underwent an intravital selenium-labeling procedure to demonstrate the somata of neurons that give rise to zinc-containing boutons. Numerous double-labeled cells were seen in the ipsi- and contralateral primary (layers II/III and VI), and secondary visual cortices (layers II/III and VI). A few double-labeled cells were apparent in other cortical areas concerned with visual processing: the orbital cortex (layers II and III), the posterior portion of the medial agranular frontal cortex (layer V/VI border), and the temporal cortex (layer VI). The cingulate, retrosplenial, perirhinal, and lateral entorhinal cortices had lamina projecting to the visual cortex and separate lamina harboring zinc-containing cells. A spatial segregation of fluorescent and zinc-containing neurons was also seen in the claustrum. This integration or segregation of projecting and zinc-containing neurons may reflect the function of the cortical areas. N-methyl-d-aspartate receptor function is antagonized by physiological concentrations of zinc in vitro. It is proposed that zinc-positive projections from areas that perform basic visual functions are less likely to be modified by N-methyl-d-aspartate receptor-mediated processes than the zinc-negative connections from associational areas.

New strategies for embedding, orientation and sectioning of small brain specimens enable direct correlation to MR-images, brain atlases, or use of unbiased stereology

We present a newly developed brain slicing machine and technique for tissue embedding, which enable orientation of fresh or fixed brain tissue from small laboratory animals, in any given position, and subsequent tissue sectioning into slabs with an optional thickness between 0.5 and 20 mm. The oriented tissue slabs may be analysed directly, or processed further on a cryostat or vibratome, into thin stainable histological sections, and aligned to MR-images or brain atlases, depending on the reference used for the initial orientation. Additionally, we describe a new embedding medium (HistOmer) which is an alginate cold polymer ready for instant use after mixing with water. HistOmer allows accurate positioning of the tissue during embedding, and at the same time supports and protects the embedded tissue during sectioning. HistOmer is, therefore, described comprehensively and compared with other commonly used embedding media. This novel slicing technique may also, as illustrated, be used to perform isotropic random orientation of the embedded tissue, before sectioning into tissue slabs of the same thickness. The technique thereby fulfills the requirements for optimal tissue sampling and preparation needed for an unbiased stereologic analysis.

New strategies for the treatment of Parkinson's disease hold considerable promise for the future management of neurodegenerative disorders

Neurodegenerative diseases are often consideredincurable with no efficient therapies to modifyor halt the progress of disease, and ultimatelylead to reduced quality of life and to death.Our knowledge of the nervous system in healthand disease has, however, increasedconsiderably during the last fifty years andtoday, neuroscience reveals promising newstrategies to deal with disorders of thenervous system.Some of these results have been implementedwith success in the treatment of Parkinsonsdisease, a common neurodegenerative illnessaffecting approximately 1% of the populationaged seventy or more. Parkinsons disease ischaracterized by a massive loss of dopaminergicneurons in the substantia nigra, leading tosevere functional disturbance of the neuronalcircuitry in the basal ganglia. A thoroughdescription of basal ganglia circuitry inhealth and disease is presented. We describehow the functional disturbances seen inParkinsons disease may be corrected atspecific sites in this circuitry by medicaltreatment or, in advanced stages of Parkinsonsdisease, by neurosurgical methods. The latterinclude lesional surgery, neuraltransplantation and deep brain stimulation,together with future treatment strategies usingdirect or indirect implantation of geneticallymodified cell-lines capable of secretingneurotrophic factors or neurotransmitters.Advantages and disadvantages are brieflymentioned for each strategy and theimplications for the future and the possibleuse of these interventions in otherneurodegenerative diseases are discussed, withspecial emphasis on deep brain stimulation.

Oriented sectioning of irregular tissue blocks in relation to computerized scanning modalities:: Results from the domestic pig brain☆

We present a new method allowing direct comparison between images obtained by present digital scanning modalities and histological sections from the same object. More specifically the paper illustrates how to orientate, embed, and section large irregular tissue blocks after magnetic resonance imaging (MRI) in such a way that accurate correlation of the digital data sets to histological sections is possible. The functionality and capability of the described procedure and slicing machine is illustrated by results from the pig brain. Accordingly, three pigs were MR-scanned, followed by perfusion fixation. The brains were removed, oriented according to the MR scans, embedded in alginate, and cut on a newly developed slicing machine. The tissue blocks were then stained to reveal grey and white matter and photographed before final sectioning on a cryostat into 80 microm thick sections which were Nissl-stained with toluidine. The results demonstrate how our method enables direct comparison between the pig brain MR images and the later obtained histological sections. The alginate embedding method and slicing machine offer the same possibilities for other parenchymateous organs and soft tissues and may, in addition, be of use in stereological analysis.

Therapeutic strategies for neurodegenerative disorders: Emerging clues from parkinson's disease

Our knowledge of Parkinsons disease pathophysiology has greatly expanded during the last century, resulting in successful new medical and neurosurgical approaches toward this common neurodegenerative disorder. These approaches might also be useable in the treatment of psychiatric disorders, which often are linked to atrophic and degenerative processes in the brain; however, the successful application of these techniques in psychiatry requires thorough elucidation of disease pathophysiology to identify proper intervention sites. Likewise, awareness of the differences between the parkinsonian and psychiatric patient populations in terms of age, disease course, and life expectancy, as well as ethical considerations might in the end determine the appropriateness of these therapeutic strategies in psychiatry.

Expression of zinc-positive cells and terminals in fetal neocortical homografts to adult rat depends on lesion type and rearing conditions

Zinc-positive neurons and terminals, known to be associated with the glutamatergic projections in the brain, can be demonstrated by the histochemical Timm method and later modifications thereof. The adult rat neocortex contain a uniform lamination of zinc-positive cells with specific projections to, e.g., the striatum. We have previously reported that fetal neocortical grafts implanted in the adult rat neocortex combined with rearing in an enriched environment can improve behavioral functions and reduce the secondary atrophy of thalamus after cortex infarction in adult rats. In order to examine whether the expression of zinc positivity is ontogenetically inherent to neocortical neurons we grafted fetal neocortical tissue to aspiration or ischemic lesions of the frontoparietal neocortex of adult rats, followed by histochemical visualization of the vesicular zinc pool by selenite or sulfide. One further aim of the study was to elucidate to what extent the distribution of zinc-containing neurons and terminals in the grafts depended on rearing under different environmental conditions. The foremost finding of the present study was that the overall density of zinc-containing terminals in fetal cortical transplants placed in brain infarcts of adult spontaneously hypertensive rats is higher when the rats are reared in an enriched environment. Moreover, the presence and expression of zinc-positive neurons and terminals do not seem to be ontogenetically inherent to the cortical neurons as the fetal neocortical grafts placed in aspiration lesions contained no zinc-selenide-positive neurons and few or no zinc-selenide-positive terminals. The presence or expression of zinc-positive cells may thus be induced by ingrowth of fibers and terminals from the host brain as transplants placed in the ischemic lesions expressed both zinc-positive neurons and terminals.

Progress and development in Parkinson disease therapy

Parkinson disease (PD) is a common neurodegenerative disorder affecting 1% of the population aged seventy or more. The causes of PD remain obscure, but basic and clinical research has led to a deep insight into PD pathophysiology, identifying several points of intervention for emerging therapeutic strategies enabling modulation of neural circuits and replacement of lost neurons, neurotransmitters, and neurotrophic factors. ∈dent In this chapter we aim, accordingly, to present a overview of the current knowledge on PD pathophysiology and demonstrate how this knowledge provides targets for current and future pharmacological and surgical treatment strategies towards PD