Dennis M. D. Landis

The organization of cytoplasm at the presynaptic active zone of a central nervous system synapse

The axoplasm at the presynaptic active zone of excitatory synapses between parallel fibers and Purkinje cell spines contains a meshwork of distinct filaments intermingled with synaptic vesicles, seen most clearly after the rapid freezing, freeze-etch technique of tissue preparation. One set of filaments extends radially from synaptic vesicles and intersects similar filaments associated with vesicles as well as larger filaments arising from the presynaptic membrane. The small, vesicle-associated filaments appear to link synaptic vesicles to one another and to enmesh them in the vicinity of the synaptic junction. The vesicle-associated filaments could be synapsin I because they have the same molecular dimensions and are distributed in the same pattern as synapsin I immunoreactivity.

The National Institutes of Health Undiagnosed Diseases Program: insights into rare diseases

Purpose:This report describes the National Institutes of Health Undiagnosed Diseases Program, details the Program’s application of genomic technology to establish diagnoses, and details the Program’s success rate during its first 2 years.Methods:Each accepted study participant was extensively phenotyped. A subset of participants and selected family members (29 patients and 78 unaffected family members) was subjected to an integrated set of genomic analyses including high-density single-nucleotide polymorphism arrays and whole exome or genome analysis.Results:Of 1,191 medical records reviewed, 326 patients were accepted and 160 were admitted directly to the National Institutes of Health Clinical Center on the Undiagnosed Diseases Program service. Of those, 47% were children, 55% were females, and 53% had neurologic disorders. Diagnoses were reached on 39 participants (24%) on clinical, biochemical, pathologic, or molecular grounds; 21 diagnoses involved rare or ultra-rare diseases. Three disorders were diagnosed based on single-nucleotide polymorphism array analysis and three others using whole exome sequencing and filtering of variants. Two new disorders were discovered. Analysis of the single-nucleotide polymorphism array study cohort revealed that large stretches of homozygosity were more common in affected participants relative to controls.Conclusion:The National Institutes of Health Undiagnosed Diseases Program addresses an unmet need, i.e., the diagnosis of patients with complex, multisystem disorders. It may serve as a model for the clinical application of emerging genomic technologies and is providing insights into the characteristics of diseases that remain undiagnosed after extensive clinical workup.Genet Med 2012:14(1):51–59

Spontaneous pyramidal cell death in organotypic slice cultures from rat hippocampus is prevented by glutamate receptor antagonists

A predictable pattern of selective neuronal cell death occurs in organotypic slice cultures of neonatal rat hippocampus during the second and third weeks in vitro. We serially examined organotypic cultures at three, four, seven, 14, 21 and 28 days in vitro, using uptake of the fluorescent dye propidium iodide to identify degenerating cells. After seven days in vitro, the cell degeneration that accompanies the slicing procedure appears to have ended. However, at 14 days in vitro, degenerating neurons could be identified in area CA3. When many degenerating cells were present in a slice, they were distributed in the dentate hilus (CA4) and proximal portions of CA1 as well. Neuronal degeneration involving mainly CA1 pyramidal cells was still apparent at 21 days in vitro, but was much less marked than at 14 days. Study of fixed cultures with light and electron microscopy methods confirmed the presence of degenerating neurons with a pyknotic or vacuolated appearance. Spontaneous neuronal degeneration at 14 and at 21 days in vitro was almost entirely prevented by the addition of 10.5 mM Mg2+ or 3 mM kynurenic acid (a glutamate receptor antagonist), beginning at seven days in vitro. Cell death was markedly decreased by treatment with 100 microM DL-2-amino-5-phosphonovaleric acid (a selective antagonist of N-methyl-D-aspartate glutamate receptors). Removal of the blocking agents by returning cultures to control media at 28 days in vitro induced widespread neuronal degeneration, involving all the regions of the hippocampal slice cultures. The inhibition of spontaneous neuronal cell death by glutamate receptor antagonists and by blockade of glutamate release at synapses suggests that the mechanism of cell death involves glutamate receptors. The time course of degeneration suggests that the vulnerability to glutamate excitotoxicity is an aspect of developmentally regulated components of glutamatergic synapses acquired in the hippocampal organotypic cultures after the first week in vitro.

Whipple disease of the nervous system

A 58-year-old man with dizziness and unsteady gait had a 10-year history of behavioral change, impotence, and a progressive peripheral neuropathy. CT revealed low-density, contrast-enhancing lesions in the right pontine tegmentum and the right medial temporal lobe. Temporal lobe biopsy contained a collection of mature histiocytes, with PAS-positive rod-shaped inclusions. These inclusions, when studied by electronmicroscopy, were seen to be membrane-bound bacilliform bodies. Peroral jejunal biopsy contained no such inclusions. Despite treatment with antibiotics, the patients neurologic illness progressed, and he succumbed to intercurrent sepsis. We believe this to be the first instance in which a lesion of Whipple disease has been identified within the CNS by CT scan, and the diagnosis made antemortem, in the absence of demonstrable systemic disease.

Intra-Arterial Thrombolytic Therapy in Peri-Coronary Angiography Ischemic Stroke

Background— Intra-arterial thrombolysis (IAT) for peri-coronary angiography (CA) stroke may be safe and efficacious. However, IAT may increase the risk of intracranial hemorrhage (ICH). Methods— A retrospective study was performed involving 3 university hospitals. All peri-CA IAT-treated cases were identified. Patient demographics, stroke severity, angiographic findings, thrombolytic use, modified Rankin Scale (mRS), ICH, and mortality were determined. Results— A total of 21 patients with post–left CA stroke were treated with IAT (mean age 71.8±12.3 years). Arterial occlusion was found in 14 (66.7%) and 7 (33.3%) of the anterior and posterior circulation, respectively. Mean time-to-therapy was 36±12 minutes from the time the neurological deficit was noted. mRS ≤2 occurred in 10 of 21 (48%) patients. Patients with younger age and shorter time-to-IAT had more complete arterial recanalization and clinical recovery. Symptomatic ICH occurred in 3 (14%) cases, and 4 (19%) patients died. Conclusions— Peri-CA IAT appears to be feasible and safe without increased risk of symptomatic ICH and death when compared with the previously reported IAT literature.

Immunocytochemical studies of substance P and leucine-enkephalin in Huntington's disease

The distribution of substance P and leucine-enkephalin in selected regions of brain obtained postmortem from patients with Huntingtons disease and from neurologically normal persons has been studied with immunocytochemical techniques. In the normal brain, substance P immunoreactivity was identified in medium-sized neurons in the neostriatum, in neurons of the external segment of the globus pallidus, and in fine fibers in teh neostriatum, inner segment of the globus pallidus, and in the pars reticulata of the substantia nigra. Huntingtons disease brains all exhibited a marked decrease in substance P fiber density in the substantia nigra and globus pallidus. A few medium-sized neurons with substance P immunoreactivity remained in the neostriatal remnant. Leucine-enkephalin immunoreactive processes were present throughout the neostriatum of normal brain, and were densely packed in the external segment of the globus pallidus and in the substantia nigra. A uniform population of medium-sized neurons containing immunoreactive leucine-enkephalin was present in the caudate and putamen. By contrast, in the Huntingtons disease brains there was a marked diminution of fiber staining in the globus pallidus and substantia nigra. A few medium-size neurons and sparse fibers with leucine-enkephalin immunoreactivity persisted in the atrophic neostriatum. These observations are consistent with previous reports of regional peptide concentrations in both normal and Huntingtons disease brain. Cells containing substance P and leucine-enkephalin immunoreactivity persist in the basal ganglia in brains from patients with Huntingtons disease, and we have no evidence that cellular content of one or the other peptide is associated with disproportionate cell death or survival.

Evidence for independent feedback control of horizontal and vertical saccades from Niemann-Pick type C disease

We measured the eye movements of three sisters with Niemann-Pick type C disease who had a selective defect of vertical saccades, which were slow and hypometric. Horizontal saccades, and horizontal and vertical pursuit and vestibular eye movements were similar to control subjects. The initial movement of oblique saccades was mainly horizontal and most of the vertical component occurred after the horizontal component ended; this resulted in strongly curved trajectories. After completion of the horizontal component of an oblique saccade, the eyes oscillated horizontally at 10-20 Hz until the vertical component ended. These findings are best explained by models that incorporate separate feedback loops for horizontal and vertical burst neurons, and in which the disease selectively affects vertical burst neurons.

Golgi and electronmicroscopic studies of spongifom encephalopathy

Golgi impregnations of cerebral biopsies from two patients suffering from Creutzfeldt-Jakob disease (subacute spongiform encephalopathy) revealed striking loss of dendritic spines of pyramidal neurons and unusual focal spherical distensions of dendritic and axonal processes. Light and electronmicroscopic studies disclosed spongiform changes, which seemed to be caused by intracytoplasmic vacuoles and expansion of the plasmalemmal membranes of neurons and astrocytes. Although the diagnostic biopsies were performed at a markedly symptomatic stage of the disease, there was no evidence of neuronal cell loss. Neuronal changes in Golgi impregnations of cerebral cortex from hamsters infected with scrapie were essentially identical to those in the human biopsies. The loss of dendritic spines of pyramidal cells and spherical swellings of axons and dendrites thus seem to be characteristic of spongiform encephalopathies, and probably account in part for the clinical neurologic manifestations, which may be severe in the relative absence of neuronal death.

Immunoreactive somatostatin in the rat retina: Light microscopic immunocytochemistry and chromatographic characterization

The retinas of adult, male Long-Evans rats contain somatostatin-like immunoreactive material (SLI) as detected by radioimmunoassay. The SLI co-chromatographs with synthetic somatostatin-14 on both gel permeation chromatography and reversed phase high performance liquid chromatography; no somatostatin-28-like material or higher molecular weight forms have been detected. Immunocytochemical methods detect SLI in at least two cell populations. The more abundant stained cells are at the inner margin of the inner nuclear layer and give off processes which form a dense meshwork of fine, varicose fibers at the outer border of the inner plexiform layer, as well as processes which pass into other sublaminas of the inner plexiform layer. Varicose immunoreactive fibers run vertically or obliquely through the inner nuclear layer and bifurcate at its outer margin, giving rise to horizontally running fibers in the outer plexiform layer. These observations are consistent with rat retinal SLI being contained within amacrine cells, at least some of which are interplexiform cells. With cholchicine pretreatment, a more sparse population of stained cells is detected in the ganglion cell layer. These cells give rise to processes which enter the inner plexiform layer. It is not known if these are ganglion cells or displaced amacrine cells.

Orthostatic limb shaking from carotid hypoperfusion

Limb shaking and other involuntary episodic movements may be a concomitant of carotid artery occlusive disease.1-3 The possibility that limb shaking can be caused by cerebral ischemia has been supported by reports of patients in whom there was no response to antiepileptic medications and an absence of epileptiform activity on ictal and interictal encephalogram, but in whom there was abnormality of cerebral blood flow. In several instances, symptoms improved after treatment with antiplatelet agents or avoiding iatrogenic hypotension.2-4 We present a patient with this unusual syndrome that was initially treated as a seizure who eventually responded to an uncommon type of endarterectomy. A 66-year-old right-handed man with a history of hypercholesterolemia, coronary artery bypass graft surgery, and pacemaker insertion for sick sinus syndrome was referred for evaluation of recurrent left-sided involuntary movement. His spells began 14 months before presentation. He repeatedly dropped keys from his hand when getting out of his car. He noted clumsiness and tremorlike motion …