X-ray contrast media induce aortic endothelial damage, which can be prevented with prior heparin treatment

X-ray contrast media induce damage to the endothelial layer of vessels and initiate the formation of thrombosis, which is a complication for clinical diagnostic procedures. The future determination of the mechanisms, which underlie the damaging effect of X-ray contrast medium on vascular wall cells, especially vascular endothelium and possible prevention of this damage by vasoprotector, will result in a larger application in diagnostic procedures. The aim of the present study is to analyze the effect of X-ray contrast media (Verographin, Iodamid and Iodolipol) on the arterial endothelium morphology by using ultrastructural techniques (scanning and transmission electron microscopy, SEM and TEM respectively). Experiments have been carried out on New Zealand white rabbits (6 month old) and Wistar rats (6-8 month old) after a single injection of X-ray contrast media with and without prior heparin treatment. Control groups of animals were exposed to the same procedure but without X-ray contrast media injection and only received isotonic saline solution. The following time points were selected: 1, 6, 24, 72 h and 7 days. At the end of the experiments, animals were anesthetized by pentobarbital and then perfused with a balanced buffer for 1 min and followed by perfusion fixation with Karnovsky's fixative containing buffered solution of 2.5% paraformaldehyde and 2.5% glutaraldehyde (pH 7.36) at least 30 min. The aortic tissue was removed and immediately placed into a fresh portion of the same fixative. Aortic samples were then prepared for scanning and transmission electron microscopy (SEM and TEM respectively). Immediately after the injection of X-ray contrast media, the number of microvilli and blebs on the luminal surface of the endothelial cells (EC) significantly increased. Very often, nuclear portions of the EC sharply protruded into the vessel lumen. Clusters of spindle-shaped EC were seen throughout the endothelial monolayer. These changes persist through the 72-h period after X-ray contrast media injection. Moreover, the desquamation and denudation of the EC from the monolayer is often observed and this is accompanied by the presence of a microthrombus on the vessel surface. Seven days after the post-injection period, endothelial monolayers still show severe damage, which often coexists with the presence of a different sized microthrombus on the vessel surface. However, the degree of lesion formation in most areas is substantially decreased as compared to the early period of post-injection (24 and 72 h). Heparin treated group shows intact morphology similar to the control experimental groups (saline injected group). Infrequently, minimal morphological changes of the endothelium, such as increased number of microblebs and microvilli, were seen with heparin treatment. We conclude that the negative side effects of the X-ray contrast media can be eliminated by a single injection of heparin or other vasoprotector prior to the diagnostic procedure.

Oxidative stress and predominant Abeta42(43) deposition in myopathies with rimmed vacuoles

This study was undertaken to determine the C terminus of amyloid beta protein (Abeta), accumulated in vacuolated muscle fibers, and compare these findings to the level of oxidative stress. Eight patients with myopathies characterized by rimmed vacuoles (RVs) were analyzed. Monoclonal antibodies specific to Abeta40 or Abeta42(43) revealed that the Abeta42(43) immunoreactivity was solely distributed in the vacuolated muscle fibers, and that only a part was also immunopositive for anti-Abeta40. Quantitative analyses in four specimens, in which eight or more vacuolated muscle fibers were observed, revealed that the mean incidence of Abeta42(43)-positive muscle fibers was 79.5+/-6.2% in total vacuolated muscle fibers, whereas that of the Abeta40-positive fibers was 42.9+/-12.6%. The predominance of Abeta42(43) deposition was statistically significant ( P<0.05). Abeta deposition was then compared with the distribution of oxidative nucleic acid damage in muscle fibers using a monoclonal antibody against 8-hydroxy-2'-deoxyguanosine and 8-hydroxyguanosine (8OHdG&G). The cytoplasmic staining for anti-8OHdG&G was found not only in vacuolated muscle fibers, but also in other muscle fibers including morphologically normal ones. Positive staining was completely abolished by RNase pretreatment and, thus, was suggested to reflect an increase of cellular RNA oxidation. The distribution of 8OHdG&G was much broader than the Abeta deposition. These data suggest that Abeta42(43) is predominantly involved in the pathogenesis of muscle fiber degeneration with RVs, and that oxidative damage may precede Abeta deposition in muscle fibers and play a key role in the pathomechanism of myopathies with RVs.

Reactive oxygen: its sources and significance in Alzheimer disease

Over the past decade, oxidative stress has been established as the earliest cytological feature of Alzheimer disease and an attractive therapeutic target. The major challenges now are establishing the source of the reactive oxygen and what oxidative stress tells us about the etiology of Alzheimer disease. These are complex issues since a variety of enzymatic and non-enzymatic processes are involved in reactive oxygen formation and damage to macromolecules. In this review, we consider disease mechanisms that show the greatest promise for future research.

Monitoring kinetic and frequency-domain properties of eyelid responses in mice with magnetic distance measurement technique

Classical eye-blink conditioning in mutant mice can be used to study the molecular mechanisms underlying associative learning. To measure the kinetic and frequency domain properties of conditioned (tone - periorbital shock procedure) and unconditioned eyelid responses in freely moving mice, we developed a method that allows adequate, absolute, and continuous determination of their eyelid movements in time and space while using an electrical shock as the unconditioned stimulus. The basic principle is to generate a local magnetic field that moves with the animal and that is picked up by either a field-sensitive chip or coil. With the use of this magnetic distance measurement technique (MDMT), but not with the use of electromyographic recordings, we were able to measure mean latency, peak amplitude, velocity, and acceleration of unconditioned eyelid responses, which equaled 7.9 +/- 0.2 ms, 1.2 +/- 0.02 mm, 28.5 +/- 1 mm/s, and 637 +/- 22 mm/s(2), respectively (means +/- SD). During conditioning, the mice reached an average of 78% of conditioned responses over four training sessions, while animals that were subjected to randomly paired conditioned and unconditioned stimuli showed no significant increases. The mean latency of the conditioned responses decreased from 222 +/- 40 ms in session 2 to 127 +/- 6 ms in session 4, while their mean peak latency increased from 321 +/- 45 to 416 +/- 67 ms. The mean peak amplitudes, peak velocities, and peak acceleration of these responses increased from 0.62 +/- 0.02 to 0.77 +/- 0.02 mm, from 3.9 +/- 0.3 to 7.7 +/- 0.5 mm/s, and from 81 +/- 7 to 139 +/- 10 mm/s(2), respectively. Power spectra of acceleration records illustrated that both the unconditioned and conditioned responses of mice had oscillatory properties with a dominant peak frequency close to 25 Hz that was not dependent on training session, interstimulus interval, or response size. These data show that MDMT can be used to measure the kinetics and frequency domain properties of conditioned eyelid responses in mice and that these properties follow the dynamic characteristics of other mammals.

Therapeutic potential in Alzheimer disease

Oxidative damage is shown to affect every class of biological macromolecule in Alzheimer disease. Disruptions in iron and copper homeostasis are understood as being key players in neurodegenerative disease pathogenesis. Metal homeostasis as it pertains to alterations in brain function in neurodegenerative diseases is reviewed here with its relations to oxidative stress. While there is substantial documented evidence for alterations in transition metal metabolism, redox-activity and localization, it is also important to note that alterations in specific copper- and iron-containing metalloenzymes also contribute to the neurodegenerative process. Understanding these changes offers the opportunity to identify pathways where modification of the disease process can offer effective clinical intervention, from gene therapy to pharmaceuticals with antioxidant and chelating properties.

Outpatient total body irradiation as a component of a comprehensive outpatient transplant program

Outpatient total body irradiation (TBI) as part of a comprehensive outpatient transplant program was delivered to 142 of 167 (85%) consecutive patients receiving TBI-based conditioning therapy. Outpatients received either a single fraction of 500 cGy (110 patients) or 1200 cGy in six fractions over 3 days (32 patients). Patients were assessed daily and were administered oral ondansetron and dexamethasone for prophylaxis of nausea and vomiting as well as i.v. hydration. Accommodation during outpatient TBI-based conditioning was either the patient's home if within 30 min of the hospital, a hotel on the hospital grounds or on a closed hospital ward. None of the 142 patients required admission to the inpatient program during their TBI. There was no difference in 100-day mortality between those receiving TBI as an outpatient (9%) vs as an inpatient (16%). Of four deaths occurring within the first 14 days post transplant, none could be attributed to receiving TBI as an outpatient. Two hundred and six inpatient days were saved through the delivery of outpatient TBI. A comprehensive outpatient program, appropriate patient selection, daily hydration, the use of prophylactic 5HT3 antagonist anti-emetic therapy all contribute to the safe delivery of outpatient TBI.

Increase of cdk5 is related to neurofibrillary pathology in progressive supranuclear palsy

BACKGROUND

Progressive supranuclear palsy (PSP) is characterized by a pure neurofibrillary tau pathology involving mainly basal ganglia and brainstem nuclei. In addition to a haplotype of the tau gene potentially favoring tau aggregation, lipoperoxidation has been shown to be associated with PSP tau pathology.

OBJECTIVE

To analyze cdk5/p35 complex, a kinase that regulates neurite outgrowth, as a potential cellular mechanism underlying tau phosphorylation in brain tissues from PSP and control cases and comparatively in cerebral cortex from subjects with AD.

METHODS

Cdk5/p35 protein levels and distribution were evaluated by immunoblotting and immunocytochemistry in brain regions from seven PSP, six AD, and seven control cases, with similar postmortem intervals.

RESULTS

Total cdk5 protein levels were significantly increased by more than threefold in PSP tissue and were augmented in PSP neurons, codistributed with tau immunoreactivity. P35, the regulatory subunit of cdk5, was degraded by postmortem proteolysis to the same extent in PSP, AD, and control tissues.

CONCLUSIONS

The proteolysis in vivo of p35, the regulatory subunit of the kinase, is not ascertainable because it is masked by its postmortem degradation. The study, however, indicates that in PSP, the alteration of cdk5 is different from that described in AD and suggests that the absence of amyloid beta protein deposition may account for the different pathways responsible for the same kinase activation.

Effect of the herbicide 4-CPA on human erythrocyte antioxidant enzymes in vitro

To investigate the possible role of oxygen free radicals and oxidant stress in the toxic effects of phenoxyherbicides, we studied the in vitro effect of 4-chlorophenoxyacetic acid (4-CPA) on various human erythrocyte antioxidant enzymes, namely glucose-6-phosphate dehydrogenase, catalase, selenium-dependent glutathione peroxidase, glutathione reductase and Cu/Zn-superoxide dismutase. 4-CPA added in a dose of 1 ppm to human erythrocytes for 1 h caused a significant reduction in glucose-6-phosphate dehydrogenase (P <0.001) and catalase (P <0.001) activities, but did not significantly affect the activities of other enzymes. Such selective inactivation of specific erythrocyte antioxidant enzymes may play a role in the toxic effects of phenoxyherbicides.

Increased expression of NOS and ET-1 immunoreactivity in human colorectal metastatic liver tumours is associated with selective depression of constitutive NOS immunoreactivity in vessel endothelium

The absence of perivascular nerves in tumour vessels suggests that endothelium derived vasoactive substances [nitric oxide (NO) and endothelin-1 (ET-1)] may be key factors in controlling tumour blood flow during tumour growth and metastasis. We have studied the ultrastructural distribution and immunoreactivity of different NO synthase (NOS) isoforms and ET-1 in human colorectal metastatic liver tumour tissues using pre-embedding peroxidase-anti-peroxidase and post-embedding immunoelectron microscopic triple gold labelling techniques. Dramatically lower NOS 1 immunoreactivity was observed in tumour vascular endothelium (1-3% and 15-20% in tumour and normal groups, respectively). As compared to control groups there were significantly less NOS3 immunopositive EC in metastatic tumour vessels (45-50% and 1-3% in normal and tumour groups, respectively). A striking rise in NOS2 was observed in tumour vessel endothelium (< 1% in normal and 65-70% in tumour vessel endothelium). ET-1 immunoreactivity levels were also significantly higher in tumour vessel endothelium (85-90% in tumour, 15-20% in normal group). This increased expression of NOS2 and ET-1 immunoreactivity was accompanied by the increased expression of three NOS isoforms and ET-1 immunoreactivity in liver parenchymal cells. These data suggest that metastatic tumour vessel endothelium is characterized by increased expression of NOS2 and ET-1 and by decreases in NOS1 and NOS3. These characteristics are associated with the overexpression of all three NOS isoforms and ET-1 immunoreactivity in non-vascular cells.

The mitochondrial common deletion in Parkinson's disease and related movement disorders

The mitochondrial 4977-bp common deletion has been reported in some studies to occur exclusively or with increased frequency in the midbrain of patients with Parkinson's disease (PD). Other studies could not confirm these results; rather, it was suggested that the mitochondrial common deletion is associated with aging in the midbrain and not PD. One possible explanation for these conflicting results is the difficulty in quantifying mitochondrial DNA deletions or mutations in the whole midbrain or substantia nigra (SN) while only a subset of midbrain neurons degenerate in PD. In addition, none of the studies has addressed the cell types with the common deletion within the midbrain. In this study we used in situ hybridization to detect the common deletion in sections of midbrain from patients with PD, multiple system atrophy-parkinsonian type (MSA-P), progressive supranuclear palsy (PSP), dementia with Lewy bodies (DLB), age-matched controls, and individuals of different ages. The results demonstrated that the mitochondrial common deletion accumulated primarily in neurons but not glia in both the SN and other midbrain regions. There was no significant difference in the number or distribution of neurons with the common deletion or the average of the mean densities (AMD) of staining with the common deletion in nigral neurons among patients with PD, MSA-P, PSP, DLB, or age-matched controls. In addition, there was no difference in the number or distribution of neurons with the common deletion in nigral neurons between any age group, although there was a tendency for the common deletion to increase in the non-nigral neurons in older patients. These data indicate that accumulation of the 4977-bp common deletion in mitochondrial DNA in midbrain occurred primarily in neurons, and by this cytological approach, it was not associated with nigral neurodegeneration in the common movement disorders or aging.

Differential activation of neuronal ERK, JNK/SAPK and p38 in Alzheimer disease: the 'two hit' hypothesis

There are multiple lines of evidence showing that oxidative stress and aberrant mitogenic signaling play an important role in the pathogenesis of Alzheimer disease. However, the chronological relationship between these and other events associated with disease pathogenesis is not known. Given the important role that mitogen-activated protein kinase (MAPK) pathways play in both mitogenic signaling (ERK) and cellular stress signaling (JNK/SAPK and p38), we investigated the chronological and spatial relationship between activated ERK, JNK/SAPK and p38 during disease progression. While all three kinases are activated in the same susceptible neurons in mild and severe cases (Braak stages III-VI), in non-demented cases with limited pathology (Braak stages I and II), both ERK and JNK/SAPK are activated but p38 is not. However, in non-demented cases lacking any sign of pathology (Braak stage 0), either ERK alone or JNK/SAPK alone can be activated. Taken together, these findings indicate that MAPK pathways are differentially activated during the course of Alzheimer disease and, by inference, suggest that both oxidative stress and abnormalities in mitotic signaling can independently serve to initiate, but both are necessary to propagate, disease pathogenesis. Therefore, we propose that both 'hits', oxidative stress and mitotic alterations, are necessary for the progression of Alzheimer disease.

Diabetes-associated sustained activation of the transcription factor nuclear factor-kappaB

Activation of the transcription factor nuclear factor-kappaB (NF-kappaB) has been suggested to participate in chronic disorders, such as diabetes and its complications. In contrast to the short and transient activation of NF-kappaB in vitro, we observed a long-lasting sustained activation of NF-kappaB in the absence of decreased IkappaBalpha in mononuclear cells from patients with type 1 diabetes. This was associated with increased transcription of NF-kappaBp65. A comparable increase in NF-kappaBp65 antigen and mRNA was also observed in vascular endothelial cells of diabetic rats. As a mechanism, we propose that binding of ligands such as advanced glycosylation end products (AGEs), members of the S100 family, or amyloid-beta peptide (Abeta) to the transmembrane receptor for AGE (RAGE) results in protein synthesis-dependent sustained activation of NF-kappaB both in vitro and in vivo. Infusion of AGE-albumin into mice bearing a beta-globin reporter transgene under control of NF-kappaB also resulted in prolonged expression of the reporter transgene. In vitro studies showed that RAGE-expressing cells induced sustained translocation of NF-kappaB (p50/p65) from the cytoplasm into the nucleus for >1 week. Sustained NF-kappaB activation by ligands of RAGE was mediated by initial degradation of IkappaB proteins followed by new synthesis of NF-kappaBp65 mRNA and protein in the presence of newly synthesized IkappaBalpha and IkappaBbeta. These data demonstrate that ligands of RAGE can induce sustained activation of NF-kappaB as a result of increased levels of de novo synthesized NF-kappaBp65 overriding endogenous negative feedback mechanisms and thus might contribute to the persistent NF-kappaB activation observed in hyperglycemia and possibly other chronic diseases.

Activation of MKK6, an upstream activator of p38, in Alzheimer's disease

Mitogen-activated protein kinase (MAPK) p38 has been implicated in the pathogenesis of Alzheimer's disease, but the upstream cascade leading to p38 activation has not been elucidated in the disease. In the present study, we focused on mitogen-activated protein kinase kinase 6 (MKK6), one of the upstream activators of p38 MAPK. We found that MKK6 was not only increased but also specifically associated with granular structures in the susceptible neurons in the hippocampus and cortex of Alzheimer's disease patients, but was only weakly diffuse in the cytoplasm in neurons in control cases. Immunoblot analysis demonstrated a significant increase of MKK6 level in Alzheimer's disease compared with age-matched controls. In this regard, in hippocampal and cortical regions of individuals with Alzheimer's disease, the activated phospho-MKK6 was localized exclusively in association with pathological alterations including neurofibrillary tangles, senile plaques, neuropil threads and granular structures, overlapping with activated p38 MAPK suggesting both a functional and mechanic link. By immunoblot analysis, phospho-MKK6 is also significantly increased in AD compared with control cases. Together, these findings lend further credence to the notion that the p38 MAPK pathway is dysregulated in Alzheimer's disease and also indicates an active role for this pathway in disease pathogenesis.

Treatment planning aids in prostate cancer: friend or foe?

BACKGROUND

Rectal barium is commonly used as a treatment planning aid for prostate cancer to delineate the anterior rectal wall. Previous research at the Ottawa Regional Cancer Centre demonstrated that retrograde urethrography results in a systematic shift of the prostate. We postulated that rectal barium could also cause prostate motion.

PURPOSE

The study was designed to evaluate the effects of rectal barium on prostate position.

METHODS AND MATERIALS

Thirty patients with cT1-T3 prostate cancer were evaluated. Three fiducial markers were placed in the prostate. During simulation, baseline posterior-anterior and lateral films were taken. Repeat films were taken after rectal barium opacification. The prostate position (identified by the fiducials) relative to bony landmarks was compared before and after rectal barium. Films were analyzed using PIPsPro software.

RESULTS

The rectal barium procedure resulted in a significant displacement of the prostate in the anterior and superior direction. The mean displacement of the prostate measured on the lateral films was 3.8 mm (SD: 4.4 mm) in the superior direction and 3.0 mm (SD: 3.1) in the anterior direction.

CONCLUSIONS

Rectal barium opacification results in a systematic shift of the prostate. This error could result in a geographic miss of the target; therefore, alternate methods of normal tissue definition should be used.

Oxidative damage is the earliest event in Alzheimer disease

Recently, we demonstrated a significant increase of an oxidized nucleoside derived from RNA, 8-hydroxyguanosine (8OHG), and an oxidized amino acid, nitrotyrosine in vulnerable neurons of patients with Alzheimer disease (AD). To determine whether oxidative damage is an early- or end-stage event in the process of neurodegeneration in AD, we investigated the relationship between neuronal 8OHG and nitrotyrosine and histological and clinical variables, i.e. amyloid-beta (A beta) plaques and neurofibrillary tangles (NFT), as well as duration of dementia and apolipoprotein E (ApoE) genotype. Our findings show that oxidative damage is quantitatively greatest early in the disease and reduces with disease progression. Surprisingly, we found that increases in A beta deposition are associated with decreased oxidative damage. These relationships are more significant in ApoE epsilon4 carriers. Moreover, neurons with NFT show a 40%-56% decrease in relative 8OHG levels compared with neurons free of NFT. Our observations indicate that increased oxidative damage is an early event in AD that decreases with disease progression and lesion formation. These findings suggest that AD is associated with compensatory changes that reduce damage from reactive oxygen.

Atherosclerotic lesions are associated with increased immunoreactivity for inducible nitric oxide synthase and endothelin-1 in thoracic aortic intimal cells of hyperlipidemic Watanabe rabbits

The development and progression of atherosclerotic lesions in Watanabe heritable hyperlipidemic rabbits is associated with increases in inducible nitric oxide synthase (NOS2) and endothelin-1 (ET-1) immunoreactivity. In contrast, there is a reduction of immunoreactivity for neuronal NOS (NOS1) in aortic endothelial cells, but no change in endothelial NOS (NOS3) immunoreactivity. However, subendothelial macrophages and smooth muscle showed a different pattern of immunoreactivity of NADPH-diaphorase (NADPH-d), NOS2, ET-1, and NOS1. The lipid-rich macrophages in the intima were positively labeled for NADPH-d, NOS1, NOS2, NOS3, and ET-1. Smooth muscle cells in the subendothelium and the medial layers of the vascular wall were also positive for these markers. These results are consistent with the reduction of endothelium-dependent vasorelaxation that is known to occur during the development and progression of atherosclerosis in familial hypercholesterolemia. The data suggest a key role for vasoactive substances in the development of atherosclerosis.

Active glycation in neurofibrillary pathology of Alzheimer disease: N(epsilon)-(carboxymethyl) lysine and hexitol-lysine

Advanced glycation end products are a diverse class of posttranslational modifications, stemming from reactive aldehyde reactions, that have been implicated in the pathogenesis of a number of degenerative diseases. Because advanced glycation end products are accelerated by, and result in formation of, oxygen-derived free radicals, they represent an important component of the oxidative stress hypothesis of Alzheimer disease (AD). In this study, we used in situ techniques to assess N(epsilon)-(Carboxymethyl)lysine (CML), the predominant advanced glycation end product that accumulates in vivo, along with its glycation-specific precursor hexitol-lysine, in patients with AD as well as in young and aged-matched control cases. Both CML and hexitol-lysine were increased in neurons, especially those containing intracellular neurofibrillary pathology in cases of AD. The increase in hexitol-lysine and CML in AD suggests that glycation is an early event in disease pathogenesis. In addition, because CML can result from either lipid peroxidation or advanced glycation, while hexitol-lysine is solely a product of glycation, this study, together with studies demonstrating the presence of 4-hydroxy-2-nonenal adducts and pentosidine, provides evidence of two distinct oxidative processes acting in concert in AD neuropathology. Our findings support the notion that aldehyde-mediated modifications, together with oxyradical-mediated modifications, are critical pathogenic factors in AD.

Induction of NADPH cytochrome P450 reductase by the Alzheimer beta-protein. Amyloid as a "foreign body"

A large body of data suggests that the Alzheimer's amyloid peptide (Abeta) causes degeneration and death of neurons by mechanisms that involve reactive oxygen species. The pathways involved in Abeta-mediated oxidative injury are only partially understood. We theorized that abnormal microaggregates and/or pathological conformations of Abeta peptides may behave as xenobiotics and trigger the induction of NADPH cytochrome P450 reductase (CP450r), an enzyme which, if induced by non-physiological substrates (such as xenobiotics like drugs or other 'foreign molecules'), is known to cause oxidative stress. In order to test this hypothesis, i.e. that Abeta can increase the expression of CP450r, SK-N-SH human neuroblastoma cells were exposed to Abeta25-35 and Abeta1-42 and then examined for induction of this enzyme in immunoblots, using specific antibodies. Following exposure to Abeta peptides, neuroblastoma cells showed a clear-cut induction of CP450r. To determine whether this mechanism is operational in vivo, we investigated the expression of CP450r in a transgenic mouse model of Alzheimer's disease (AD) and in brains from patients afflicted with AD, using an immunocytochemical approach. Tissue sections from brains of transgenic mice exhibited strong immunoreactivity for CP450r, surrounding amyloid deposits. The pattern of expression of CP450r was similar to that exhibited by neuritic and oxidative stress markers. Sections from non-transgenic mice showed no detectable immunoreactivity. Immunostaining of sections from four brains with neuropathologically confirmed AD showed a pattern of abnormality different from transgenic mice that was characterized by abnormal immunoreactivity for CP450r within the cytoplasm of cortical neurons. No labeling was seen in sections from aged-matched control brains. The data showed that CP450r is induced by Alzheimer amyloid peptide and that such a response must be considered as one possible mechanism whereby Abeta causes oxidative stress.

Chemistry and Biochemistry of Oxidative Stress in Neurodegenerative Disease

The age-related neurodegenerative diseases exemplified by Alzheimer&hyp;s disease (AD), Lewy body diseases such as Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), and Huntington&hyp;s disease are characterized by the deposition of abnormal forms of specific proteins in the brain. Although several factors appear to underlie the pathological depositions, the cause of neuronal death in each disease appears to be multifactorial. In this regard, evidence in each case for a role of oxidative stress is provided by the finding that the pathological deposits are immunoreactive to antibodies recognizing protein side-chains modified either directly by reactive oxygen or nitrogen species, or by products of lipid peroxidation or glycoxidation. Although the source(s) of increased oxidative damage are not entirely clear, the findings of increased localization of redox-active transition metals in the brain regions most affected is consistent with their contribution to oxidative stress. It is tempting to speculate that free radical oxygen chemistry plays a pathogenetic role in all these neurodegenerative conditions, though it is as yet undetermined what types of oxidative damage occur early in pathogenesis, and what types are secondary manifestations of dying neurons. Delineation of the profile of oxidative damage in each disease will provide clues to how the specific neuronal populations are differentially affected by the individual disease conditions.