The impact of a fellow on a regional robotic-assisted partial nephrectomy service.

INTRODUCTION: Training a fellow has a cost in time and effort for the surgeon and their team. Their relative inexperience may also negatively affect the patient. The aim of this study was to determine and quantify the impact of a fellow on a regional robotic-assisted partial nephrectomy service and on perioperative outcomes. MATERIALS AND METHODS: We reviewed the prospectively collected data for 522 patients who had undergone robotic-assisted partial nephrectomy since 2015 during the tenure of six fellows. Perioperative outcomes for three groups were compared: group A (no fellow participation), group B (some participation) and group C (fellow completed entire operation). We also reviewed progression over 12 months. RESULTS: Demographics were similar in all groups apart from the percentage of men, which was lower in group C (p < 0.05). Operative time was 27 minutes longer for group B (p < 0.001). Warm ischaemia time was significantly shorter for group A but the difference was only four minutes (p < 0.001). Length of stay was slightly shorter for group C compared with the other groups (p < 0.01). Trifecta achievement was greatest for group A (p < 0.001). There were no perioperative deaths in any group and positive margins, complications and readmissions were low and similar in all groups. Towards the end of their fellowship, fellows performed more operations independently. CONCLUSION: There is a measurable, but small, negative impact of a fellow on a robotic-assisted partial nephrectomy service, which reduces with experience. With appropriate supervision and patient selection, a fellow can be taught robotic-assisted partial nephrectomy without affecting patient safety or treatment outcome.

Congruence and trajectories of device-measured and self-reported physical activity during therapy for early breast cancer.

PURPOSE: This study examines congruence between self-reported and device-measured physical activity data in women with early breast cancer and compares trajectories under different treatments. METHODS: Women with non-metastatic breast cancer were recruited before primary therapy. In four weeks distributed over six months after treatment start, patients reported time spent on work, transport, chores and sports via diary and wore Garmin® vivofit 3 accelerometers to assess steps taken. Associations between these measures and agreement regarding guideline adherence were tested with Spearman's Correlation Coefficient and Weighted Kappa statistic. Effects of time and treatment were evaluated using mixed analyses of variance. RESULTS: Ninety-nine participants (median age = 50) were treated with adjuvant (N = 23), neoadjuvant (N = 21) or without chemotherapy (N = 55). Coherence between self-report and device data was strong (r = 0.566). Agreement about reaching recommendations was only "fair" (kappa coefficient = 0.321 and 0.249, resp.). Neither treatment or week nor their interaction had effects on step counts (all p > 0.05). Self-reported activity time was lower for patients with chemotherapy than for those without (adjuvant: ∆ = 69min, p = 0.006, neoadjuvant: ∆ = 45min, p = 0.038) and lower in week 18 than in week 3 (∆ = 43min, p = 0.010). CONCLUSION: Results show that consumer-grade activity monitors and self-reports correlate but show different perspectives on physical activity in breast cancer patients. In general, patients perceive some decline regardless of primary treatment regimen. Those affected should be offered assistance to gain the benefits of activity. Accelerometers may help professionals to identify these individuals and patients to verify appraisal of their activity levels.

Alignment sensing for optical cavities using radio-frequency jitter modulation.

Alignment sensing is often required in precision interferometry applications such as Advanced LIGO in order to achieve the optimum performance. Currently favored sensing schemes rely on the use of two separate radio-frequency (RF) quadrant photodetectors and Gouy phase telescopes to determine the alignment of a beam relative to an optical cavity axis. In this paper, we demonstrate an alternative sensing scheme that has potential advantages over the current standard schemes. We show that by using electro-optic beam deflectors to impose RF jitter sidebands on a beam, it is possible to extract full alignment signals for two in-line optical cavities from just one single-element photodetector in reflection of each cavity.

Delivering kidney cancer care in rural Central and Southern Illinois: a telemedicine approach.

There is a growing body of experience and research suggesting that telemedicine (video conferencing, smart phones and online patient portals) could be the solution to addressing gaps in the provision of specialised healthcare in rural areas. The proposed role of telemedicine in providing needed services in hard to reach areas is not new. The United States Telecommunication Act of 1996 provided the initial traction for telemedicine by removing important economic and legal obstacles regarding the use of technology in healthcare delivery. This initial ruling has been supplemented by the availability of federal funding to support efforts aimed at developing telemedicine in underserved areas. In this paper, we explore one aspect of disease disparity pertinent to rural Illinois (kidney cancer incidence and mortality) and describe how we are planning to use an existing telemedicine program at Southern Illinois University School of Medicine (SIUSOM) to improve kidney cancer (Kca) care in rural Illinois. This represents an example of the possible role of telemedicine in addressing healthcare disparities in rural areas/communities and provides a description of general challenges and barriers to the implementation and maintenance of such systems.

Cardiac characterization of 16 patients with large NF1 gene deletions.

The aim of this study was to characterize cardiac features of patients with neurofibromatosis 1 (NF1) and large deletions of the NF1 gene region. The study participants were 16 patients with large NF1 deletions and 16 age- and sex-matched NF1 patients without such deletions. All the patients were comprehensively characterized clinically and by echocardiography. Six of 16 NF1 deletion patients but none of 16 non-deletion NF1 patients have major cardiac abnormalities (p = 0.041). Congenital heart defects (CHDs) include mitral insufficiency in two patients and ventricular septal defect, aortic stenosis, and aortic insufficiency in one patient each. Three deletion patients have hypertrophic cardiomyopathy. Two patients have intracardiac tumors. NF1 patients without large deletions have increased left ventricular (LV) diastolic posterior wall thickness (p < 0.001) and increased intraventricular diastolic septal thickness (p = 0.001) compared with a healthy reference population without NF1, suggestive of eccentric LV hypertrophy. CHDs and other cardiovascular anomalies are more frequent among patients with large NF1 deletion and may cause serious clinical complications. Eccentric LV hypertrophy may occur in NF1 patients without whole gene deletions, but the clinical significance of this finding is uncertain. All patients with clinical suspicion for NF1 should be referred to a cardiologist for evaluation and surveillance.

The impact of regional deprivation and individual socio-economic status on the prevalence of Type 2 diabetes in Germany. A pooled analysis of five population-based studies.

AIM: Our objective was to test the hypothesis that the prevalence of Type 2 diabetes increases with increasing regional deprivation even after controlling for individual socio-economic status. METHODS: We pooled cross-sectional data from five German population-based studies. The data set contained information on n = 11,688 study participants (men 50.1%) aged 45-74 years, of whom 1008 people had prevalent Type 2 diabetes (men 56.2%). Logistic multilevel regression was performed to estimate odds ratios (OR) and 95% confidence intervals (CI) for diabetes prevalence. We controlled for sex, age and lifestyle risk factors, individual socio-economic status and regional deprivation, based on a new small-area deprivation measure, the German Index of Multiple Deprivation. RESULTS: Adjusted for sex, age, body mass index (BMI), physical activity, smoking status and alcohol consumption, the prevalence of Type 2 diabetes showed a stepwise increase in risk with increasing area deprivation [OR 1.88 (95% CI 1.16-3.04) in quintile 4 and OR 2.14 (95% CI 1.29-3.55) in quintile 5 compared with the least deprived quintile 1], even after controlling for individual socio-economic status. Focusing on individual socio-economic status alone, the risk of having diabetes was significantly higher for low compared with medium or high educational level [OR 1.46 (95% CI 1.24-1.71)] and for the lowest compared with the highest income group [OR 1.53 (95% CI 1.18-1.99)]. CONCLUSION: Regional deprivation plays a significant part in the explanation of diabetes prevalence in Germany independently of individual socio-economic status. The results of the present study could help to target public health measures in deprived regions.

International spinal cord injury pulmonary function basic data set.

OBJECTIVES: To develop the International Spinal Cord Injury (SCI) Pulmonary Function Basic Data Set within the framework of the International SCI Data Sets in order to facilitate consistent collection and reporting of basic bronchopulmonary findings in the SCI population. SETTING: International. METHODS: The SCI Pulmonary Function Data Set was developed by an international working group. The initial data set document was revised on the basis of suggestions from members of the Executive Committee of the International SCI Standards and Data Sets, the International Spinal Cord Society (ISCoS) Executive and Scientific Committees, American Spinal Injury Association (ASIA) Board, other interested organizations and societies and individual reviewers. In addition, the data set was posted for 2 months on ISCoS and ASIA websites for comments. RESULTS: The final International SCI Pulmonary Function Data Set contains questions on the pulmonary conditions diagnosed before spinal cord lesion,if available, to be obtained only once; smoking history; pulmonary complications and conditions after the spinal cord lesion, which may be collected at any time. These data include information on pneumonia, asthma, chronic obstructive pulmonary disease and sleep apnea. Current utilization of ventilator assistance including mechanical ventilation, diaphragmatic pacing, phrenic nerve stimulation and Bi-level positive airway pressure can be reported, as well as results from pulmonary function testing includes: forced vital capacity, forced expiratory volume in one second and peak expiratory flow. The complete instructions for data collection and the data sheet itself are freely available on the website of ISCoS (http://www.iscos.org.uk).

NorthernLights in slide-based cytometry and microscopy.

In recent years, slide-based cytometry has become a key technology for polychromatic cytometric investigations, and many efforts have been made to increase the number of measurable fluorochromes for multiparametric analysis. Sequential photobleaching of fluorochromes next to very photostable dyes is one approach for this technology. As the ALEXA dyes are known to be photostable as compared to the conventional fluorochromes FITC, PE (Riggs et al., Am J Pathol 1958;34:1081-1097), and APC, a differentiation within a fluorochrome pair is possible. Here, we have analyzed the newly available NorthernLights secondary antibodies for use in slide-based cytometry and microscopy. Currently, these fluorochrome-conjugates are now available with three distinct excitation- and emission maxima (NL493, NL557, NL637). Their spectral properties are similar to the frequently used fluorochromes FITC, PE, and APC and can, therefore, be used with most common excitation sources of cytometers or microscopes. As the NorthernLights are bright, resistant to photobleaching, stable in alcohols and xylene and of affordable price, these dyes are promising candidates for use with most laser- and HBO/XBA-based fluorescence microscopy-like techniques.

Cysts in the cyst pattern.

The increased knowledge of the natural course of cystic echinococcosis has also improved our understanding of the typical imaging features ("cysts in the cyst pattern") which can be nicely shown by imaging modalities, e. g., ultrasound and computed tomography. In the very early stages of echinococcosis without calcifications, ultrasound can depict the specific intralesional morphology in detail.

Chemokine and chemokine receptor expression analysis in target organs of acute graft-versus-host disease.

Acute graft-versus-host disease (aGVHD) is a major complication after allogeneic bone marrow transplantation (allo-BMT), and infiltration of donor leukocytes into aGVHD target organs is partially orchestrated by chemokines. Using a murine BMT model, the expression of 30 chemokines or chemokine receptors in the lung, liver, gut and tongue was analyzed using real-time PCR at 1, 2, 3 and 6 weeks after BMT during the development of clinical aGVHD and target organ histopathology. CXCL9-11 expression was linked to elevated expression of CXCR3 in the gut, lung and tongue. In contrast, hepatic CXCR3 expression was not changed, whereas a clear association was seen for CXCL16 and CXCR6 expression. An elevated intestinal CCL3 expression 1 week after allo-BMT was associated with an increased expression of CCR5 but not CCR1 or CCR3, and in the lung and liver CCL3-CCL5 expression was associated with increases in CCR1 and CCR5. Overexpression of CCL2, CCL8, CCL12 and their receptor CCR2 was found in the liver and lung, but not in the gut and tongue. On the basis of the differences in kinetics and organ distribution, more studies are required to better characterize specific targets within this network, as this will allow the development of novel preventive and therapeutic approaches by using single or multiple targeting reagents.

In vivo imaging in experimental preclinical tumor research--a review.

The multiparametric molecular cell and tissue analysis in vitro and in vivo is characterized by rapid progress in the field of image generation technologies, sensor biotechnology, and computational modeling. Fascinating new potentials in unraveling the detailed functions of single cells, organs, and whole organisms are presently emerging and permit the close monitoring i.e. tumor development or basic cell development processes with an unprecedented multiplicity of promising investigative possibilities. To answer basic questions of in vivo tumor development and progression fluorescence based imaging techniques provide new insights into molecular pathways and targets. Genetic reporter systems (eGFP, DsRED) are available and high sensitive detection systems are on hand. These techniques could be used for in vitro assays and quantified e.g. by microscopy and CCD based readouts. The introduction of novel fluorescent dyes emitting in the near infrared range (NIR) combined with the development of sensitive detector systems and monochromatic powerful NIR-lasers for the first time permits the quantification and imaging of fluorescence and/or bioluminescence in deeper tissues. Laser based techniques particularly in the NIR-range (like two-photon microscopy) offer superb signal to noise ratios, and thus the potential to detect molecular targets in vivo. In combination with flat panel volumetric computed tomography (fpVCT), questions dealing e.g. with tumor size, tumor growth, and angiogenesis/vascularization could be answered noninvasively using the same animal. The resolution of down to 150 microm/each direction can be achieved using fpVCT. It is demonstrated by many groups that submillimeter resolutions can be achieved in small animal imaging at high sensitivity and molecular specificity. Since the resolution in preclinical small animal imaging is down to approximately 10 microm by the use of microCT and to subcellular resolutions using ( approximately 1 microm) microscope based systems, the advances of different techniques can now be combined to "multimodal" preclinical imaging and the possibilities for in vivo intravital cytometry now become within one's reach.

Effective treatment of hepatitis C-associated immune-complex nephritis with cryoprecipitate apheresis and antiviral therapy.

A 38-year-old pregnant woman (19th week of pregnancy) complained of fatigue, cold inducible paresthesias, generalized edema and mild arterial hypertension. Her past medical history was notable for frequent episodes of polyarthralgia and positivity for rheumatoid factor. On admission, acanthocyturia and unselective glomerular-tubular proteinuria with 19 g/d were detected with a slight decrease in creatinine clearance. Rheumatoid factor was robustly elevated and a cryocrit of 1.5 vol%, caused by a so far unknown replicative hepatitis C, was detected. Renal biopsy yielded membrano-proliferative glomerulonephritis. During pregnancy, high-dose corticosteroid therapy was administered. Edema disappeared and blood pressure normalized under albumin substitution and low-dose furosemide application. However, Cesarian section became necessary due to placental insufficiency at 27 weeks of gestation. Thereafter, neither virus load, cryocrit nor proteinuria decreased significantly under a combined therapy with pegylated interferon-a and ribavirin. Thus, cryoprecipitate apheresis was initiated resulting in robust decreases of clinical complaints, viral load, cryocrit and proteinuria. Cryoglobulinemia with renal involvement caused by hepatitis C is difficult to treat due to limitations of immunosuppressive and anti-viral therapy. In our patient, cryoprecipitate apheresis was a safe and effective therapeutic addition to standard therapy.

SCF modulates organ distribution and hematopoietic engraftment of CB-derived pluripotent HPC transplanted in NOD/SCID mice.

BACKGROUND: During the engraftment process of transplanted HPC, the beta 1 integrins play an important role. An increased expression and adhesive function of these integrins has been shown in hematopoietic cell lines and peripheral blood-derived HPC after stimulation with SCF. In this study, we investigated the influence of SCF on the engraftment capability and tissue distribution of cord blood (CB) cells transplanted into NOD/SCID mice. METHODS: CB-derived mononuclear cells were injected i.v. into 40 sublethally irradiated NOD/SCID mice with or without the addition of 10 microg SCF/ mouse. Six weeks later, BM, liver, kidneys, brain and testicular tissue were analyzed for the prevalence of human cells. RESULTS: The mean proportion of human CD45+ CD71+ cells within the BM of all engrafted mice receiving SCF in addition to the cells was 1.7-fold higher than in the respective controls. By immunohistochemical staining, human cells were found in liver and kidneys of the engrafted animals, but not in neural tissues or testicles. In the kidneys, the proportion of human cells rose significantly from 0.07 +/- 0.3% to 0.24 +/- 0.05% with treatment with SCF, compared with untreated controls. Single human cells in the liver additionally stained positive for human albumin, indicating organ-specific differentiation of the transplanted cells. DISCUSSION: Our results indicate that stimulation with SCF modulates the tissue distribution of the progeny of the transplanted cells and improves the hematopoietic engraftment potential of transplanted CB cells.

Characterization of simian virus 40 on its infectious entry pathway in cells using fluorescence correlation spectroscopy.

SV40 (simian virus 40) is a double-stranded DNA virus and is strongly oncogenic in experimental animals. SV40 enters cells by atypical endocytosis mediated by caveolae, transporting the virus to its usual destination, namely the endoplasmic reticulum. The cellular mechanisms of capsid disassembly (uncoating) and deliverance of the viral genome into the cellular nucleus remain unknown. Here, we study (i) the formation of caveolae after viral infection and the diffusion of caveosome vesicles in the cytoplasm and (ii) the capsid disassembly and the mobility of the viral genome on its way to the nucleus, using fluorescence correlation spectroscopy. To follow the viral genome and capsids separately, the histone components of SV40 minichromosomes were labelled with enhanced yellow fluorescent protein and the capsid was labelled with a fluorescent red dye, Alexa568. We characterized the diffusion of caveosomes, the capsid disassembly process in the cytoplasm and the mobility of the viral genome in the nucleus, using two kinds of permissive cells.

Impact of smoking on the response to treatment of thyroid associated ophthalmopathy.

BACKGROUND: In patients with Graves' disease, smoking considerably increases the incidence and severity of thyroid associated ophthalmopathy (TAO). The authors sought to determine if smoking also influences the course of TAO during treatment, and the efficacy of therapy. METHODS: 41 smokers and 19 non-smokers with moderate untreated TAO were included in this prospective study. All patients were treated with steroids and, 6 weeks after the beginning of drug therapy, with orbital irradiation. Follow up was performed 1.5, 4.5, 7.5, and 12 months after the beginning of the study. Proptosis, clinical activity score (CAS), and motility were evaluated. The extent of smoking was derived from the concentration of the haemoglobin adduct N-2-hydroxyethylvaline (HEV), a parameter of long term smoking. RESULTS: There was no difference in the clinical manifestations of TAO between smokers and non-smokers at the beginning of treatment. However, CAS decreased (p<0.05) and motility improved (p<0.02) significantly faster and to a greater extent in non-smokers than smokers. Inverse correlations between the CAS decrease and the HEV levels observed 4.5 and 7.5 months after the beginning of treatment and between the improvement of motility and the HEV levels after 1.5, 4.5, and 7.5 months indicated a dose dependence. Mean HEV levels did not vary much during the follow up period and were significantly different in smokers (mean 5.4 (SD 2.7) micro g/l) and non-smokers (mean 1.8 (1.3) micro g/l; p<0.01). CONCLUSION: Smoking influences the course of TAO during treatment in a dose dependent manner. The response to treatment is delayed and considerably poorer in smokers.

Comparison of a neural net-based QSAR algorithm (PCANN) with Hologram- and multiple linear regression-based QSAR approaches: application to 1,4-dihydropyridine-based calcium channel antagonists.

A QSAR algorithm (PCANN) has been developed and applied to a set of calcium channel blockers which are of special interest because of their role in cardiac disease and also because many of them interact with P-glycoprotein, a membrane protein associated with multidrug resistance to anticancer agents. A database of 46 1,4-dihydropyridines with known Ca2+ channel binding affinities was employed for the present analysis. The QSAR algorithm can be summarized as follows: (1) a set of 90 graph theoretic and information theoretic descriptors representing various structural and topological characteristics was calculated for each of the 1,4-dihydropyridines and (2) principal component analysis (PCA) was used to compress these 90 into the eight best orthogonal composite descriptors for the database. These eight sufficed to explain 96% of the variance in the original descriptor set. (3) Two important empirical descriptors, the Leo-Hansch lipophilic constant and the Hammet electronic parameter, were added to the list of eight. (4) The 10 resulting descriptors were used as inputs to a back-propagation neural network whose output was the predicted binding affinity. (5) The predictive ability of the network was assessed by cross-validation. A comparison of the present approach with two other QSAR approaches (multiple linear regression using the same variables and a Hologram QSAR model) is made and shows that the PCANN approach can yield better predictions, once the right network configuration is identified. The present approach (PCANN) may prove useful for rapid assessment of the potential for biological activity when dealing with large chemical libraries.

Clinical disorders of bone resorption.

Clinical disorders in which bone resorption is increased are very common and include Paget's disease of bone, osteoporosis, and the bone changes secondary to cancer, such as occur in myeloma and metastases from breast cancer. Clinical disorders of reduced bone resorption are less common and often have a genetic basis, e.g. in osteopetrosis, and in pycnodysostosis due to cathepsin K deficiency. Bone is metabolically active throughout life. After skeletal growth is complete, remodelling of both cortical and trabecular bone continues and results in an annual turnover of about 10% of the adult skeleton. The commonest disorder of bone resorption is osteoporosis, which affects one in three women over 50 years. Its pathophysiological basis includes genetic predisposition and subtle alterations in systemic and local hormones, coupled with environmental influences. Treatment depends mainly on drugs that inhibit bone resorption, either directly or indirectly. This includes bisphosphonates, oestrogens, synthetic oestrogen-related compounds (SERMs--selective oestrogen receptor modulators) and calcitonin. The most widely used drugs for all disorders of increased bone resorption, including osteoporosis, are the bisphosphonates. Recent elucidation of their mode of action, together with the rapidly increasing knowledge of regulatory mechanisms in bone biology, offers many opportunities for the development of new therapeutic agents.

Global folds of proteins with low densities of NOEs using residual dipolar couplings: application to the 370-residue maltodextrin-binding protein.

The global fold of maltose-binding protein in complex with the substrate beta-cyclodextrin was determined by solution NMR methods. The two-domain protein is comprised of a single polypeptide chain of 370 residues, with a molecular mass of 42 kDa. Distance information in the form of H(N)-H(N), H(N)-CH(3) and CH(3)-CH(3) NOEs was recorded on (15)N, (2)H and (15)N, (13)C, (2)H-labeled proteins with methyl protonation in Val, Leu, and Ile (C(delta1) only) residues. Distances to methyl protons, critical for the structure determination, comprised 77 % of the long-range restraints. Initial structures were calculated on the basis of 1943 NOEs, 48 hydrogen bond and 555 dihedral angle restraints. A global pair-wise backbone rmsd of 5.5 A was obtained for these initial structures with rmsd values for the N and C domains of 2.4 and 3.8 A, respectively. Direct refinement against one-bond (1)H(N)-(15)N, (13)C(alpha)-(13)CO, (15)N-(13)CO, two-bond (1)H(N)-(13)CO and three-bond (1)H(N)-(13)C(alpha) dipolar couplings resulted in structures with large numbers of dipolar restraint violations. As an alternative to direct refinement against measured dipolar couplings we have developed an approach where discrete orientations are calculated for each peptide plane on the basis of the dipolar couplings described above. The orientation which best matches that in initial NMR structures calculated from NOE and dihedral angle restraints exclusively is used to refine further the structures using a new module written for CNS. Modeling studies from four different proteins with diverse structural motifs establishes the utility of the methodology. When applied to experimental data recorded on MBP the precision of the family of structures generated improves from 5.5 to 2.2 A, while the rmsd with respect to the X-ray structure (1dmb) is reduced from 5.1 to 3.3 A.

Induction of peptidylglycine alpha-amidating monooxygenase in N(18)TG(2) cells: a model for studying oleamide biosynthesis.

The fatty-acid primary amide, oleamide, is a novel signaling molecule whose mechanism of biosynthesis is unknown. Recently, the N(18)TG(2) cell line was shown to synthesize oleamide from oleic acid, thereby demonstrating that these cells contain the necessary catalytic activities for generating the fatty-acid primary amide. The ability of peptide alpha-amidating enzyme, peptidylglycine-alpha-amidating monooxygenase (PAM; EC 1.14.17.3), to catalyze the formation of oleamide from oleoylglycine in vitro suggests this as a function for the enzyme in vivo. This investigation shows that N(18)TG(2) cells, in fact, express PAM and that cellular differentiation dramatically increases this expression. PAM expression was confirmed by the detection of PAM mRNA, PAM protein, and enzymatic activity that exhibits the functional characteristics of PAM isolated from mammalian neuroendocrine tissues. The regulated expression of PAM in N(18)TG(2) cells is consistent with the proposed role of PAM in the biosynthesis of fatty-acid primary amides and further establishes this cell line as a model for studying the pathway.

Mice deficient in cellular glutathione peroxidase show increased vulnerability to malonate, 3-nitropropionic acid, and 1-methyl-4-phenyl-1,2,5,6-tetrahydropyridine.

Glutathione peroxidase (GSHPx) is a critical intracellular enzyme involved in detoxification of hydrogen peroxide (H(2)O(2)) to water. In the present study we examined the susceptibility of mice with a disruption of the glutathione peroxidase gene to the neurotoxic effects of malonate, 3-nitropropionic acid (3-NP), and 1-methyl-4-phenyl-1,2,5,6-tetrahydropyridine (MPTP). Glutathione peroxidase knock-out mice showed no evidence of neuropathological or behavioral abnormalities at 2-3 months of age. Intrastriatal injections of malonate resulted in a significant twofold increase in lesion volume in homozygote GSHPx knock-out mice as compared to both heterozygote GSHPx knock-out and wild-type control mice. Malonate-induced increases in conversion of salicylate to 2,3- and 2, 5-dihydroxybenzoic acid, an index of hydroxyl radical generation, were greater in homozygote GSHPx knock-out mice as compared with both heterozygote GSHPx knock-out and wild-type control mice. Administration of MPTP resulted in significantly greater depletions of dopamine, 3,4-dihydroxybenzoic acid, and homovanillic acid in GSHPx knock-out mice than those seen in wild-type control mice. Striatal 3-nitrotyrosine (3-NT) concentrations after MPTP were significantly increased in GSHPx knock-out mice as compared with wild-type control mice. Systemic 3-NP administration resulted in significantly greater striatal damage and increases in 3-NT in GSHPx knock-out mice as compared to wild-type control mice. The present results indicate that a knock-out of GSHPx may be adequately compensated under nonstressed conditions, but that after administration of mitochondrial toxins GSHPx plays an important role in detoxifying increases in oxygen radicals.