Know DBS: patient perceptions and knowledge of deep brain stimulation in Parkinson's disease

Introduction

Deep brain stimulation (DBS) is an established therapy for Parkinson's disease (PD) that can significantly improve motor symptoms and quality of life. Despite its effectiveness, little is known about patient perceptions of DBS.

Objectives

To evaluate patient perceptions of DBS for PD, focusing on understanding, satisfaction, and factors influencing their outlook. This study aims to enhance patient education and counseling by identifying key determinants of patient perceptions.

Design

A patient survey.

Methods

We surveyed 77 PD patients who had undergone DBS at multiple centers using a comprehensive questionnaire. The questionnaire included questions on demographic information, disease history, and detailed understanding about the indications for DBS, side effects, outlook, and other common misconceptions. We summarize data using measures of central tendency and dispersion appropriate to the data type (categorical, continuous, proportional) and model relationships among variables using fractional and linear regression methods.

Results

Participants had a median age of 66 years, were predominantly male (66%), Caucasian (90%), well-educated (79% with at least college degrees), and had a disease duration of greater than 5 years (97%). They conveyed good understanding of the signs and symptoms addressed by DBS across the motor and non-motor domains and associated side effects. Regression analysis identified age, disease duration, and education level as key determinants of patient understanding and outlook of DBS.

Conclusion

Our study provides a detailed understanding of patient perceptions of DBS for PD, including the benefits, challenges, and misconceptions. Our findings underscore the importance of identifying the causes of disparities in patient knowledge and perceptions regarding DBS to tailor patient counseling and ensure optimal treatment outcomes.

Serum thyroid-stimulating hormone and interleukin-8 levels in boys with autism spectrum disorder

Background

Autism spectrum disorder (ASD) affects approximately 1 in 68 children in the USA. An ASD blood biomarker may enable early diagnosis and/or identification of new therapeutic targets. Serum samples from ASD and typically developing (TD) boys (n = 30/group) were screened for differences in 110 proteins using a multiplex immunoassay.

Results

Eleven proteins were found that together could confirm ASD with modest accuracy using multiple training and test sets. Two of the 11 proteins identified here were further tested using a different detection platform and with a larger sample of ASD and TD boys. The two proteins, thyroid-stimulating hormone (TSH) and interleukin-8 (IL-8), have been previously identified as putative biomarkers for ASD. TSH levels were significantly lower in ASD boys, whereas IL-8 levels were significantly elevated. The diagnostic accuracy for ASD based upon TSH or IL-8 levels alone varied from 74 to 76%, but using both proteins together, the diagnostic accuracy increased to 82%. In addition, TSH levels were negatively correlated with the Autism Diagnostic Observation Schedule subdomain scores.

Conclusions

These data suggest that a panel of proteins may be useful as a putative blood biomarker for ASD.

A Search for Blood Biomarkers for Autism: Peptoids

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by impairments in social interaction and communication, and restricted, repetitive patterns of behavior. In order to identify individuals with ASD and initiate interventions at the earliest possible age, biomarkers for the disorder are desirable. Research findings have identified widespread changes in the immune system in children with autism, at both systemic and cellular levels. In an attempt to find candidate antibody biomarkers for ASD, highly complex libraries of peptoids (oligo-N-substituted glycines) were screened for compounds that preferentially bind IgG from boys with ASD over typically developing (TD) boys. Unexpectedly, many peptoids were identified that preferentially bound IgG from TD boys. One of these peptoids was studied further and found to bind significantly higher levels (>2-fold) of the IgG1 subtype in serum from TD boys (n = 60) compared to ASD boys (n = 74), as well as compared to older adult males (n = 53). Together these data suggest that ASD boys have reduced levels (>50%) of an IgG1 antibody, which resembles the level found normally with advanced age. In this discovery study, the ASD1 peptoid was 66% accurate in predicting ASD.

Administration of thimerosal-containing vaccines to infant rhesus macaques does not result in autism-like behavior or neuropathology

Autism spectrum disorder (ASD) is a complex neurodevelopmental disorder. Some anecdotal reports suggest that ASD is related to exposure to ethyl mercury, in the form of the vaccine preservative, thimerosal, and/or receiving the measles, mumps, rubella (MMR) vaccine. Using infant rhesus macaques receiving thimerosal-containing vaccines (TCVs) following the recommended pediatric vaccine schedules from the 1990s and 2008, we examined behavior, and neuropathology in three brain regions found to exhibit neuropathology in postmortem ASD brains. No neuronal cellular or protein changes in the cerebellum, hippocampus, or amygdala were observed in animals following the 1990s or 2008 vaccine schedules. Analysis of social behavior in juvenile animals indicated that there were no significant differences in negative behaviors between animals in the control and experimental groups. These data indicate that administration of TCVs and/or the MMR vaccine to rhesus macaques does not result in neuropathological abnormalities, or aberrant behaviors, like those observed in ASD.

Inducible neuronal inactivation of Sim1 in adult mice causes hyperphagic obesity

Germline haploinsufficiency of human or mouse Sim1 is associated with hyperphagic obesity. Sim1 encodes a transcription factor required for proper formation of the paraventricular (PVN), supraoptic, and anterior periventricular hypothalamic nuclei. Sim1 expression persists in these neurons in adult mice, raising the question of whether it plays a physiologic role in regulation of energy balance. We previously showed that Sim1 heterozygous mice had normal numbers of PVN neurons that were hyporesponsive to melanocortin 4 receptor agonism and showed reduced oxytocin expression. Furthermore, conditional postnatal neuronal inactivation of Sim1 also caused hyperphagic obesity and decreased hypothalamic oxytocin expression. PVN projections to the hindbrain, where oxytocin is thought to act to modulate satiety, were anatomically intact in both Sim1 heterozygous and conditional knockout mice. These experiments provided evidence that Sim1 functions in energy balance apart from its role in hypothalamic development but did not rule out effects of Sim1 deficiency on postnatal hypothalamic maturation. To address this possibility, we used a tamoxifen-inducible, neural-specific Cre transgene to conditionally inactivate Sim1 in adult mice with mature hypothalamic circuitry. Induced Sim1 inactivation caused increased food and water intake and decreased expression of PVN neuropeptides, especially oxytocin and vasopressin, with no change in energy expenditure. Sim1 expression was not required for survival of PVN neurons. The results corroborate previous evidence that Sim1 acts physiologically as well as developmentally to regulate body weight. Inducible knockout mice provide a system for studying Sim1's physiologic function in energy balance and identifying its relevant transcriptional targets in the hypothalamus.

Mical links semaphorins to F-actin disassembly

How instructive cues present on the cell surface have their precise effects on the actin cytoskeleton is poorly understood. Semaphorins are one of the largest families of these instructive cues and are widely studied for their effects on cell movement, navigation, angiogenesis, immunology and cancer. Semaphorins/collapsins were characterized in part on the basis of their ability to drastically alter actin cytoskeletal dynamics in neuronal processes, but despite considerable progress in the identification of semaphorin receptors and their signalling pathways, the molecules linking them to the precise control of cytoskeletal elements remain unknown. Recently, highly unusual proteins of the Mical family of enzymes have been found to associate with the cytoplasmic portion of plexins, which are large cell-surface semaphorin receptors, and to mediate axon guidance, synaptogenesis, dendritic pruning and other cell morphological changes. Mical enzymes perform reduction-oxidation (redox) enzymatic reactions and also contain domains found in proteins that regulate cell morphology. However, nothing is known of the role of Mical or its redox activity in mediating morphological changes. Here we report that Mical directly links semaphorins and their plexin receptors to the precise control of actin filament (F-actin) dynamics. We found that Mical is both necessary and sufficient for semaphorin-plexin-mediated F-actin reorganization in vivo. Likewise, we purified Mical protein and found that it directly binds F-actin and disassembles both individual and bundled actin filaments. We also found that Mical utilizes its redox activity to alter F-actin dynamics in vivo and in vitro, indicating a previously unknown role for specific redox signalling events in actin cytoskeletal regulation. Mical therefore is a novel F-actin-disassembly factor that provides a molecular conduit through which actin reorganization-a hallmark of cell morphological changes including axon navigation-can be precisely achieved spatiotemporally in response to semaphorins.

Crk-associated substrate (Cas) signaling protein functions with integrins to specify axon guidance during development

Members of the Cas family of Src homology 3 (SH3)-domain-containing cytosolic signaling proteins are crucial regulators of actin cytoskeletal dynamics in non-neuronal cells; however, their neuronal functions are poorly understood. Here, we identify a Drosophila Cas (DCas), find that Cas proteins are highly expressed in neurons and show that DCas is required for correct axon guidance during development. Functional analyses reveal that Cas specifies axon guidance by regulating the degree of fasciculation among axons. These guidance defects are similar to those observed in integrin mutants, and genetic analysis shows that integrins function together with Cas to facilitate axonal defasciculation. These results strongly support Cas proteins working together with integrins in vivo to direct axon guidance events.

5HTTLPR polymorphism and enlargement of the pulvinar: unlocking the backdoor to the limbic system

BACKGROUND

The 5HTTLPR genetic variant of the serotonin transporter (SERT), which consists of a long (SERT-l) and short (SERT-s) allele, has emerged as a major factor influencing emotional behavior and brain anatomy. The pulvinar nucleus of the thalamus projects to important limbic nuclei including the amygdala and cingulate cortex, is involved in the processing of stimuli with emotional content, and contains an abundance of SERT.

METHODS

Stereological methods were used to measure pulvinar neuron number in postmortem tissue from major depressive disorder (n = 11), bipolar disorder (n = 11), schizophrenia (n = 12), and control (n = 15) specimens from the Stanley Foundation Neuropathology Consortium. The effect of SERT genotype on pulvinar volume and neuron number was investigated by using analysis of covariance.

RESULTS

Analysis of covariance with diagnosis, SERT genotype, age, hemisphere, postmortem interval, and time-in-formalin covariates identified a 20% increase in pulvinar neuron number and volume in SERT-ss subjects.

CONCLUSIONS

The elevated number of pulvinar neurons in subjects with a SERT-ss genotype may serve to enhance subcortical input of emotionally relevant stimuli to the limbic system, providing a mechanism for the 5HTTLPR genetic variant to affect predisposition to conditions such as major depression.

Rat model of Parkinson's disease: Chronic central delivery of 1-methyl-4-phenylpyridinium (MPP+)

Mitochondrial dysfunction is observed in sporadic Parkinson's disease (PD) and may contribute to progressive neurodegeneration. While acute models of mitochondrial dysfunction have been used for many years to investigate PD, chronic models may better replicate the cellular disturbances caused by long-standing mitochondrial derangements and may represent a better model for neurotherapeutic testing. This study sought to develop a chronic model of PD that has the advantages of continuous low level toxin delivery, low mortality, unilateral damage to minimize aphagia and adipsia as well as minimal animal handling to reduce stress-related confounds. Infusion by osmotic minipump of the complex I toxin, 1-methyl-4-phenylpyridinium (MPP+), for 28 days into the left cerebral ventricle in rats caused a selective ipsilateral loss of nigral tyrosine hydroxylase immunoreactive somata (35% loss). In animals that were sacrificed 14 days after the chronic MPP+ administration, there was an even greater loss of nigral tyrosine hydroxylase cells (65% loss). Lewy-body-like structures that stained positive for ubiquitin and alpha-synuclein were found in striatal neurons near the infusion site but were not observed in nigral neurons. At the electron microscope level, however, swollen and abnormal mitochondria were observed in the nigral dopamine neurons, which may represent the early formation of an inclusion body. There were no animal deaths with the chronic treatment regimen that was utilized, and the magnitude of nigrostriatal neuronal loss was relatively consistent among the animals. This model of progressive neurodegeneration of nigrostriatal dopamine neurons may be useful for studying neuroprotective therapeutic agents for PD.

Decreased adult hippocampal neurogenesis in the PDAPP mouse model of Alzheimer's disease

Abnormal subgranular zone (SGZ) neurogenesis is proposed to contribute to Alzheimer's disease (AD)-related decreases in hippocampal function. Our goal was to examine hippocampal neurogenesis in the PDAPP mouse, a model of AD with age-dependent accumulation of amyloid-beta(42) (Abeta(42))-containing plaques that is well studied with regard to AD therapies. A secondary goal was to determine whether altered neurogenesis in the PDAPP mouse is associated with abnormal maturation or number of mature cells. A tertiary goal was to provide insight into why hippocampal neurogenesis appears to be increased in AD post-mortem tissue and decreased in most AD mouse models. We report an age-dependent decrease in SGZ proliferation in homozygous PDAPP mice. At 1 year of age, PDAPP mice also had new dentate gyrus granule neurons with abnormal maturation and fewer dying cells relative to control mice. In contrast to decreased SGZ cell birth, PDAPP mice had increased birth of immature neurons in the outer portion of the granule cell layer (oGCL), providing insight into why some studies link AD with increased neurogenesis. However, these ectopic oGCL cells were still rare compared with SGZ proliferating cells, emphasizing that the primary characteristic of PDAPP mice is decreased neurogenesis. The decrease in SGZ neurogenesis was not associated with an age-dependent loss of dentate granule neurons. The altered neurogenesis in the PDAPP mouse may contribute to the age-related cognitive deficits reported in this model of AD and may be a useful adjunct target for assessing the impact of AD therapies.

The semaphorins

Semaphorins are secreted, transmembrane, and GPI-linked proteins, defined by cysteine-rich semaphorin protein domains, that have important roles in a variety of tissues. Humans have 20 semaphorins, Drosophila has five, and two are known from DNA viruses; semaphorins are also found in nematodes and crustaceans but not in non-animals. They are grouped into eight classes on the basis of phylogenetic tree analyses and the presence of additional protein motifs. The expression of semaphorins has been described most fully in the nervous system, but they are also present in most, or perhaps all, other tissues. Functionally, semaphorins were initially characterized for their importance in the development of the nervous system and in axonal guidance. More recently, they have been found to be important for the formation and functioning of the cardiovascular, endocrine, gastrointestinal, hepatic, immune, musculoskeletal, renal, reproductive, and respiratory systems. A common theme in the mechanisms of semaphorin function is that they alter the cytoskeleton and the organization of actin filaments and the microtubule network. These effects occur primarily through binding of semaphorins to their receptors, although transmembrane semaphorins also serve as receptors themselves. The best characterized receptors for mediating semaphorin signaling are members of the neuropilin and plexin families of transmembrane proteins. Plexins, in particular, are thought to control many of the functional effects of semaphorins; the molecular mechanisms of semaphorin signaling are still poorly understood, however. Given the importance of semaphorins in a wide range of functions, including neural connectivity, angiogenesis, immunoregulation, and cancer, much remains to be learned about these proteins and their roles in pathology and human disease.

Double-knockout mice for alpha- and beta-synucleins: effect on synaptic functions

An abundant presynaptic protein, alpha-synuclein, is centrally involved in the pathogenesis of Parkinson's disease. However, conflicting data exist about the normal function of alpha-synuclein, possibly because alpha-synuclein is redundant with the very similar beta-synuclein. To investigate the functions of synucleins systematically, we have now generated single- and double-knockout (KO) mice that lack alpha- and/or beta-synuclein. We find that deletion of synucleins in mice does not impair basic brain functions or survival. We detected no significant changes in the ultrastructure of synuclein-deficient synapses, in short- or long-term synaptic plasticity, or in the pool size or replenishment of recycling synaptic vesicles. However, protein quantitations revealed that KO of synucleins caused selective changes in two small synaptic signaling proteins, complexins and 14-3-3 proteins. Moreover, we found that dopamine levels in the brains of double-KO but not single-KO mice were decreased by approximately 20%. In contrast, serotonin levels were unchanged, and dopamine uptake and release from isolated nerve terminals were normal. These results show that synucleins are not essential components of the basic machinery for neurotransmitter release but may contribute to the long-term regulation and/or maintenance of presynaptic function.

Elevated neuron number in the limbic thalamus in major depression

OBJECTIVE

The mediodorsal and anteroventral/anteromedial nuclei of the thalamus are brain regions of interest in the study of mood disorders because they connect subcortical limbic system structures such as the amygdala with the prefrontal, cingulate, and temporal cortices. Anatomical abnormalities have been observed both in the amygdala and in the aforementioned cortical regions in affective disorder patients. Neuroanatomical studies of the thalamus have rarely been conducted in patients with mood disorders.

METHOD

Postmortem tissue from the Stanley Foundation Brain Bank was obtained from subjects diagnosed with major depressive disorder, bipolar disorder, and schizophrenia as well as a nonpsychiatric comparison group (N=10-13 per group). The optical disector stereological procedure was used to count neurons in the mediodorsal and anteroventral/anteromedial nuclei of the thalamus in each brain.

RESULTS

There were significantly more neurons in the mediodorsal (37%) and anteroventral/anteromedial (26%) nuclei in subjects with major depressive disorder relative to the nonpsychiatric comparison subjects. Neuron numbers and volumes in these limbic thalamic nuclei were normal in the schizophrenia and bipolar subjects.

CONCLUSIONS

The data indicate that there is an elevation in total neuron number in the limbic thalamus that is specific for major depressive disorder. This represents the first report of a neuropsychiatric disorder being associated with an increase in total regional neuron number. The present findings, along with recent data, indicate that significant anatomical and functional abnormalities are present in limbic circuits in major depressive disorder.

Inverse relationship between the contents of neuromelanin pigment and the vesicular monoamine transporter-2: human midbrain dopamine neurons

The dopaminergic neurons in the ventral substantia nigra (SN) are significantly more vulnerable to degeneration in Parkinson's disease (PD) than the dopaminergic neurons in the ventral tegmental area (VTA). The ventral SN neurons also contain significantly more neuromelanin pigment than the dopaminergic neurons in the VTA. In vitro data indicate that neuromelanin pigment is formed from the excess cytosolic catecholamine that is not accumulated into synaptic vesicles by the vesicular monoamine transporter-2 (VMAT2). By using quantitative immunohistochemical methods in human postmortem brain, we sought to examine the relative contents of VMAT2 within neurons that contain different amounts of neuromelanin pigment. The immunostaining intensity (ISI) was measured for VMAT2 and also for the rate-limiting enzyme for the synthesis of dopamine, tyrosine hydroxylase (TH). ISI measures were taken from the ventral SN region where neurons are most vulnerable to degeneration in PD, nigrosome-1 (N1); from the ventral SN region where cells are moderately vulnerable to degeneration in PD, the matrix (M); and from VTA neurons near the exit of the third nerve (subregion III). The data indicate that 1) subregion III neurons have significantly higher levels of VMAT2 ISI compared with N1 neurons (more than twofold) and M neurons (45%); 2) there is an inverse relationship between VMAT2 ISI and neuromelanin pigment in the N1 and III neurons; 3) there is an inverse relationship between VMAT2 ISI and the vulnerability to degeneration in PD in the N1, M, and III subregions; and 4) neurons with high VMAT2 ISI also have high TH ISI. These data support the hypothesis that midbrain dopaminergic neurons that synthesize greater amounts of dopamine have more vesicular storage capacity for action potential-induced release of transmitter and that the ventral SN neurons accumulate the most neuromelanin pigment, in part because they have the least VMAT2 protein.

Cholinergic neuropathology in a mouse model of Alzheimer's disease

Transgenic mice overexpressing mutant human amyloid precursor protein (PDAPP mice) develop several Alzheimer's disease (AD)-like lesions including an age-related accumulation of amyloid-beta (Abeta)-containing neuritic plaques. Although aged, heterozygous PDAPP mice also exhibit synaptic and glial cell changes characteristic of AD pathology, no evidence of widespread neuronal loss has been observed. The present study sought to determine whether homozygous PDAPP mice, which express very high levels of Abeta peptide, exhibit AD-like cholinergic degenerative changes, and whether the changes parallel the deposition of Abeta plaques. Mice were examined at 2 and 4 months and at 1 and 2 years of age. There was an age-related increase in the density of Abeta plaques in the cortex and hippocampus of the PDAPP animals; at 4 months of age there were very few plaques, and at 2 years there was a very high density of plaques. There was an age-related reduction in the density of cholinergic nerve terminals in the cerebral cortex; at 2 months there was a normal density of nerve terminals, but as early as age 4 months there was an approximately 50% reduction. However, at age 2 years there was no difference in the number or size of basal forebrain cholinergic somata compared with 2-month-old PDAPP mice. These data indicated that the homozygous PDAPP mouse exhibits cholinergic nerve terminal degenerative pathology and that the cortical neurodegenerative changes occur before the deposition of Abeta-containing neuritic plaques.

Validation of a near-infrared probe for detection of thin intracranial white matter structures

OBJECT

The authors have developed an intracranial near-infrared (NIR) probe that analyzes the scattering of light emitted from its tip to measure the optical properties of cerebral tissue. Despite its success in distinguishing graymatter from white matter in humans during stereotactic surgery, the limits of this instrument's resolution remain unclear. In this study, the authors determined the spatial resolution of this new probe by using a rodent model supplemented with phantom measurements and computer simulation.

METHODS

A phantom consisting of Intralipid and gelatin was constructed to resemble a layer of white matter overlying a layer of gray matter. Near-infrared measurements were obtained as the probe was inserted through the gray-white matter transition. A computer simulation of NIR measurements through a gray-white matter transition was also performed using Monte Carlo techniques. The NIR probe was then used to study 19 tracks from the cortical surface through the corpus callosum in an in vivo rodent preparation. The animals were killed and histological sections through the tracks were obtained. Data from the phantom models and computer simulations showed that the NIR probe samples a volume of tissue extending 1 to 1.5 mm in front of the probe tip (this distance is termed the "lookthrough" distance). Measurements obtained from an NIR probe passing through a thin layer of white matter consisted of an initial segment of increasing values, a maximum (peak) value, and a trailing segment of decreasing values. The length of the initial segment is the lookthrough distance, the position of the peak indicates the location of the superficial white matter boundary, and the length of the trailing segment is the thickness of the layer. These considerations were confirmed in experiments with rodents. All tracks passed through the corpus callosum, which was demonstrated as a broad peak on each NIR graph. The position of the dorsal boundary of the corpus callosum and its width (based on histological measurements) correlated well with the peak of the NIR curve and its trailing segment, respectively. The initial segments correlated well with estimates of the lookthrough distance. Five of the tracks transected the smaller anterior commissure (diameter 0.2 mm), producing a narrow NIR peak at the correct depth.

CONCLUSIONS

Data in this study confirm that the NIR probe can reliably detect and measure the thickness of layers of white matter as thin as 0.2 mm. Such resolution should be adequate to detect larger structures of interest encountered during stereotactic surgery in humans.

Neurodegeneration in the Niemann-Pick C mouse: glial involvement

A mouse model of Niemann-Pick type C disease has been found that exhibits neuropathology similar to the human condition. There is an age-related neurodegeneration in several brain regions and a lack of myelin in the corpus callosum in these mice. The purpose of the present study was to examine the Niemann-Pick mouse and determine whether: (1) microglia and astrocytes exhibit ultrastructural pathology similar to that found in neurons; (2) nerve fiber number is reduced when the myelin sheath is absent; and (3) the lysosomal hydrolase, cathepsin-D, is involved in the neurodegenerative process. Using light and electron microscopic methods, and immunocytochemistry, Niemann-Pick and control animals were examined at several ages. Cathepsin-D content was semi-quantitatively measured in neurons and glial cells in brain regions known to exhibit neurodegeneration, as was the density of glial fibrillary acidic protein-labeled astrocytes. The Niemann-Pick mouse exhibited: (1) an age-related increase in inclusion bodies in microglia and astrocytes, similar to that observed within neurons; (2) an almost complete absence of myelin in the corpus callosum by 7-8 weeks of age, along with a 30% reduction in the number of corpus callosum axons; (3) a mild age-related increase in cathepsin-D content within nerve cells in many brain regions. However, the cathepsin-D elevation was greatest in microglial cells; (4) an age-related increase in the number of microglial cells containing intense cathepsin-D immunoreactivity in both the thalamus and cerebellum. Both of these brain regions have been shown previously to exhibit an age-related loss of neurons; and (5) an increase in the number of reactive astrocytes immunostained for glial fibrillary acidic protein, especially in the thalamus and cerebellum. These data indicate that glial cells are a major target for pathology in the Niemann-Pick mouse. The lack of myelin within the corpus callosum may be related to the loss of nerve fibers in this structure. The increase in cathepsin-D-laden microglial cells, in brain regions previously shown to undergo neurodegeneration, is consistent with a role for microglia in the phagocytosis of dead neurons and in actively contributing to the neurodegenerative process. The activation of astrocytes in regions that undergo neurodegeneration is also consistent with a role for these glial cells in the neurodegenerative process.