Michael S. Pollanen

Parietal Pick's disease mimicking cortical-basal ganglionic degeneration

We report a patient with pathologically proven asymmetric Picks disease involving the parietal lobe who displayed a combination of parkinsonism, myoclonus, and other motor disturbances more typical of cortical-basal ganglionic degeneration.

Cortical degeneration in progressive supranuclear palsy. A comparison with cortical-basal ganglionic degeneration.

We report 3 patients with progressive supranuclear palsy (PSP) who developed limb apraxia, focal dystonia, and arm levitation late in the course of the disease. Neuropathological examination revealed cortical degeneration in addition to the characteristic pathological findings of PSP. Semiquantitative comparative histological and immunohistological studies of the neocortex of these patients as well as 5 cases of classical PSP and 4 cases of cortical-basal ganglionic degeneration (CBGD) revealed a distinctive form of cortical degeneration in PSP. The cortical degeneration was often circumscribed and confined to premotor and motor cortex. It was characterized by neuronal loss and gliosis. Swollen neurons were only rarely observed in neocortex of PSP cases in contrast with CBGD, where they were abundant. Neuronal and glial tau as well as tau immunoreactive threads were seen in both PSP and CBGD, but were more abundant in CBGD. The appearance of tau reactive astrocytes also differed in both disorders; tufted astrocytes were seen exclusively in PSP, while typical annular astrocytic plaques were confined to CBGD. These observations indicate that cortical degeneration occurs in PSP and may be associated with atypical clinical manifestations that lead to diagnostic difficulties.

Sequential assembly of collagen revealed by atomic force microscopy

Most polymers which comprise biological filaments assemble by two mechanisms: nucleation and elongation or a sequential, stepwise process involving a hierarchy of intermediate species. We report the application of atomic force microscopy (AFM) to the study of the early events in the sequential or stepwise mode of assembly of a macromolecular filament. Collagen monomers were assembled in vitro and the early structural intermediates of the assembly process were examined by AFM and correlated with turbidimetric alterations in the assembly mixture. The assembly of collagen involved a sequence of distinctive filamentous species which increased in both diameter and length over the time course of assembly. The first discrete population of collagen oligomers were 1-2 nm in diameter (300-500 nm in length); at later time points, filaments approximately 2-6 nm in diameter (> 10 microns in length) many with a conspicuous approximately 67-nm axial period were observed. Occasional mature collagen fibrils with a approximately 67-nm axial repeat were found late in the course of assembly. Our results are consistent with initial end-to-end axial association of monomers to form oligomers followed by lateral association into higher-order filaments. On this basis, there appears to be at least two distinctive types of structural interactions (axial and lateral) which are operative at different levels in the assembly hierarchy of collagen.

The Diagnostic Value of the Diatom Test for Drowning, I. Utility: A Retrospective Analysis of 771 Cases of Drowning in Ontario, Canada

The utility and validity of the diatom test for drowning was studied using a retrospective analysis of 771 cases of drowning mostly from Ontario, Canada, over the period 1977 to 1993. In this article (part one), the utility of the test was assessed using an analysis of test outcomes. In the companion article (part two), the validity of the test was assessed by analyzing the relationship between test outcome and characteristics of diatoms in the bone marrow and samples of putative drowning medium. In the present study, freshwater drownings accounted for 738 of the cases and 33 cases were drownings in bathtubs, pools, or toilets. Diatoms were recovered from the femoral bone marrow of 205 cases (28%) of freshwater drowning and four cases (12%) of domestic water drowning. There was a monthly variation in the frequency of positive test outcomes that could not be explained by seasonal differences in the total number of drownings. However, the monthly variation was strongly correlated with the periodic cycle of diatom blooms that occurs in freshwater. Positive diatom tests were characterized by a limited number of distinctive diatom species per case, and a restricted quantity and size range of diatom frustules. These results indicate that the diatom test for drowning will identify approximately one in three victims of freshwater drowning and may be useful in the assessment of deaths occurring in bathtubs. The correlation of the outcome of the diatom test for drowning with diatom blooms provides further evidence for the reliability of the test.

Fracture of the hyoid bone in strangulation: comparison of fractured and unfractured hyoids from victims of strangulation.

The hyoid is the U-shaped bone of the neck that is fractured in one-third of all homicides by strangulation. On this basis, postmortem detection of hyoid fracture is relevant to the diagnosis of strangulation. However, since many cases lack a hyoid fracture, the absence of this finding does not exclude strangulation as a cause of death. The reasons why some hyoids fracture and others do not may relate to the nature and magnitude of force applied to the neck, age of the victim, nature of the instrument (ligature or hands) used to strangle, and intrinsic anatomic features of the hyoid bone. We compared the case profiles and xeroradiographic appearance of the hyoids of 20 victims of homicidal strangulation with and without hyoid fracture (n = 10, each). The fractured hyoids occurred in older victims of strangulation (39 +/- 14 years) when compared to the victims with unfractured hyoids (30 +/- 10 years). The age-dependency of hyoid fracture correlated with the degree of ossification or fusion of the hyoid synchondroses. The hyoid was fused in older victims of strangulation (41 +/- 12 years) whereas the unfused hyoids were found in the younger victims (28 +/- 10 years). In addition, the hyoid bone was ossified or fused in 70% of all fractured hyoids, but, only 30% of the unfractured hyoids were fused. The shape of the hyoid bone was also found to differentiate fractured and unfractured hyoids. Fractured hyoids were longer in the anterior-posterior plane and were more steeply sloping when compared with unfractured hyoids. These data indicate that hyoids of strangulation victims, with and without fracture, are distinguished by various indices of shape and rigidity. On this basis, it may be possible to explain why some victims of strangulation do not have fractured hyoid bones.

Diatoms and homicide

Six illustrative cases of homicidal drowning are reported in which the diatom test for drowning was a useful adjunct to the medicolegal investigation of death. In all six cases, diatom frustules were recovered from the femoral bone marrow. In five cases, diatoms extracted from the bone marrow were compared with diatoms obtained from samples of putative drowning medium. In all of these case, the same types of diatoms were observed in both the water samples and the marrow. In an additional case, watery fluid from the maxillary sinus contained the same diatom types as were present in the femoral bone marrow. Four of the six cases were found submerged in water and had autopsy findings consistent with drowning. In the remaining two cases, the bodies were found on land; one case was grossly decomposed and one body was extensively burned since the body was set afire on dry land after death. In some of the case drowning was associated with blunt force head injury (one case), sharp force injuries of the chest (one case), or strangulation (three cases). These results indicate that the diatom test for drowning is an important adjunct to the medicolegal investigation of homicidal drowning, particularly in those cases were autopsy and scene findings do not imply drowning as a cause of death.

Characterization of a shared epitope in cortical Lewy body fibrils and Alzheimer paired helical filaments

The straight fibrils of the Lewy body contain an epitope related to phosphorylation of the KSPV motif common to the C termini of the 200- and 170-kDa neurofilament subunits and τ. To further characterize this phosphorylated neurofilament/τ epitope in Lewy bodies and to analyze the constituents of isolated Lewy bodies we used a combined biochemical and immunochemical approach. In formalin-fixed paraffin-embedded tissue cortical Lewy bodies were labelled by monoclonal antibodies directed to phosphorylation-dependent KSPV epitopes in the sequences of neurofilament and phosphorylation-independent epitopes. Immunoblotting of solubilized Lewy body fibrils with the same antibodies which stained Lewy bodies in tissue sections revealed that the immunoreactive Lewy body proteins were phosphorylated neurofilament subunits. An antibody to the 68-kDa neurofilament subunit labelled Lewy bodies and Lewy body protein at 50–68 kDa. We conclude that the shared phosphorylated epitope in Lewy body fibrils and paired helical filaments is related to the common KSPV sequence in neurofilament and τ, and that all three neurofilament subunits are present in the Lewy body. This result indicates that although Lewy bodies and neurofibrillary tangles share epitopes they are comprised of distinct structural subunits.

Detergent‐Insoluble Cortical Lewy Body Fibrils Share Epitopes with Neurofilament and τ

Abstract: Lewy bodies are cytoskeletal inclusions associated with neuronal injury and death in idiopathic Parkinsons disease and other neurodegenerative disorders. The chemical composition of the 8–10‐nm fibrils of the Lewy body is unknown, although they are related to both normal cytoskeletal elements and paired helical filaments of Alzheimer neurofibrillary tangles. From the Lewy body‐rich cerebral cortex of patients with diffuse Lewy body disease we have isolated intact Lewy bodies using a high salt buffer/nonionic detergent gradient centrifugation procedure and extracted the constitutive fibrils with urea and sodium dodecyl sulfate. Urea/detergent‐resistant Lewy body fibrils were solubilized with formic acid and found to contain a single protein band of 68 kDa, which was not found in identically prepared normal brain homogenates. The Lewy body derived‐polypeptide was recognized on immunoblots by a polyclonal antibody that reacted with both the 68‐kDa neurofilament subunit and the microtubule‐associated protein τ. The 68‐kDa Lewy body protein was not labeled by the monoclonal antibody τ‐1 despite prior in vitro enzymatic dephosphorylation. We conclude that the detergent‐insoluble component of the cortical Lewy body fibril shares epitopes with neurofilament and τ and may be a posttranslationally modified derivative of either neurofilament or τ with substantially altered biochemical and immunologic properties.

The Location of Hyoid Fractures in Strangulation Revealed by Xeroradiography

The location of 19 fractures of 15 hyoid bones was studied from 13 cases of manual strangulation and two cases of hanging. The precise location of the fractures were determined by xeroradiography of isolated hyoid bones. To classify the location of the fractures, the greater cornu was divided into anterior, middle, and posterior thirds and the frequency of fracture occurrence in these locations was determined. In addition, the angle of curvature of the greater cornu was determined at the fracture site to ascertain if specific points along the greater cornu were more susceptible to fracture. Fractures were found with equal frequency in the posterior and middle thirds of the hyoid greater cornu (9/19, 47% for both posterior and middle) but were rare in the anterior portion (1/19, 5%). However, all fractures occurred between 30 degrees and 60 degrees of curvature of the hyoid and most fractures (approximately 60%) were found at approximately 50 degrees. These results indicate that fractures of the hyoid occur at vulnerable angles of curvature of the hyoid bone which, due to anatomic variation in hyoid shape, do not necessarily occur at specific segments of the hyoid bone. On this basis, although the presence of the hyoid fracture in strangulation is determined by the rigidity of the bone, the specific location is determined by the shape of the greater cornu.

Paired helical filaments are twisted ribbons composed of two parallel and aligned components: image reconstruction and modeling of filament structure using atomic force microscopy.

To study the structure of Alzheimer paired helical filaments (PHF) we examined isolated detergent-insoluble PHF using atomic force microscopy with image reconstruction. The reconstructed AFM images of Alzheimer PHF most closely resembled ribbon-like helices with thin edges. The presence of a conspicuous furrow in the PHF midline indicated that PHF were composed of two distinctive strands. Our present conception of the overall configuration of PHF is consistent with that proposed by Crowther and Wischik in 1985 but includes an essential component of the prevailing model: the presence of two strands. Thus, our new model of PHF structure, based on atomic force microscopy-derived data, indicates that the true structure of PHF is actually a hybrid of the prevailing PHF model and a thin helical ribbon.