Factors related to genetic testing in adults at risk for Huntington disease: the prospective Huntington at-risk observational study (PHAROS).

Huntington disease (HD) is a late onset ultimately fatal neurodegenerative disorder caused by a cytosine-adenine-guanine ( CAG) triplet repeat expansion in the Huntingtin gene which was discovered in 1993. The PHAROS study is a unique observational study of 1001 individuals at risk for HD who had not been previously tested for HD and who had no plans to do so. In this cohort, 104 (10%) individuals changed their minds and chose to be tested during the course of the study but outside of the study protocol. Baseline behavioral scores, especially apathy, were more strongly associated with later genetic testing than motor and chorea scores, particularly among subjects with expanded CAG repeat length. In the CAG expanded group, those choosing to be tested were older and had more chorea and higher scores on the behavioral section of the unified Huntington's disease rating scale at baseline than those not choosing to be tested. Following genetic testing, 56% of subjects with CAG < 37 had less depression when compared to prior to testing, but depression generally stayed the same or increased for 64% of subjects in the expanded group. This finding suggests that approaches to testing must continue to be cautious, with appropriate medical, psychological and social support.

Relationship Between Hyperglycemia and Heart Transplant Rejection.

PURPOSE: Hyperglycemia increases risks of kidney and liver transplant rejection. To determine whether perioperative and subsequent glycemic control was associated with increased risk of heart transplant rejection over the year after transplantation, we performed a retrospective analysis of glycemic control and rejection rates in heart transplantation patients. METHODS: Perioperative glucose levels were analyzed in 157 patients undergoing transplantation at Northwestern Memorial Hospital from June 2005 to December 2012 and compared in patients with and without rejection found on routine follow-up biopsy specimens. RESULTS: Grade ≤1R rejection on biopsy was observed in 116 patients and grade ≥2R rejection (grade requiring increased anti-rejection treatment) in 41 patients. Although no significant differences in the preoperative fasting or inpatient mean glucose levels were found, the mean glucose levels from discharge to 1 year trended higher in those with grade ≥2R compared to grade ≤1R (128.8 ± 40.9 versus 142.2 ± 46.6 mg/dL, P = .084). In a multivariable logistic regression model, neither the lowest nor highest quartile of glucose levels had significantly different odds ratios (ORs) for the development of ≥2R compared to the middle 50% glucose levels. Older age (OR 0.96, P = .020) and higher body mass index levels (OR 0.86, P = .004) were significantly associated with lower odds of developing grade ≥2R. CONCLUSIONS: Although the glucose trend regarding rejection was not statistically significant, we cannot exclude the possibility that much higher glucose levels would influence rejection rates.

Antipsychotic drugs cause bradycardia in GD 13 rat embryos in vitro.

This study investigated the effects of antipsychotic drugs on heart function of gestational day (GD) 13 rat embryos in vitro since they all block the I(Kr)/hERG potassium ion channel in addition to their main pharmacological effect on neurotransmitters. The results showed that all the tested antipsychotic drugs caused bradycardia of the rat embryonic heart in a concentration-dependent manner. However, with the possible exception of haloperidol the tested drugs did not cause arrhythmias typically seen with the highly selective I(Kr)/hERG blocking drug dofetilide. For six of the eight drugs tested the effects on the embryonic rat heart were only seen at free drug concentrations that were much greater than those likely to occur in pregnant women taking antipsychotic medication. However, the safety margins for haloperidol and quetiapine were lower.

Dietary intake in adults at risk for Huntington disease: analysis of PHAROS research participants.

OBJECTIVE: To examine caloric intake, dietary composition, and body mass index (BMI) in participants in the Prospective Huntington At Risk Observational Study (PHAROS). METHODS: Caloric intake and macronutrient composition were measured using the National Cancer Institute Food Frequency Questionnaire (FFQ) in 652 participants at risk for Huntington disease (HD) who did not meet clinical criteria for HD. Logistic regression was used to examine the relationship between macronutrients, BMI, caloric intake, and genetic status (CAG <37 vs CAG > or =37), adjusting for age, gender, and education. Linear regression was used to determine the relationship between caloric intake, BMI, and CAG repeat length. RESULTS: A total of 435 participants with CAG <37 and 217 with CAG > or =37 completed the FFQ. Individuals in the CAG > or =37 group had a twofold odds of being represented in the second, third, or fourth quartile of caloric intake compared to the lowest quartile adjusted for age, gender, education, and BMI. This relationship was attenuated in the highest quartile when additionally adjusted for total motor score. In subjects with CAG > or =37, higher caloric intake, but not BMI, was associated with both higher CAG repeat length (adjusted regression coefficient = 0.26, p = 0.032) and 5-year probability of onset of HD (adjusted regression coefficient = 0.024; p = 0.013). Adjusted analyses showed no differences in macronutrient composition between groups. CONCLUSIONS: Increased caloric intake may be necessary to maintain body mass index in clinically unaffected individuals with CAG repeat length > or =37. This may be related to increased energy expenditure due to subtle motor impairment or a hypermetabolic state.

Genotoxicity studies of a desealant solvent mixture, SR-51.

The Royal Australian Air Force (RAAF) has reported that personnel involved in F-111 fuel tank maintenance were concerned that exposure to a range of chemicals during the period 1977 to mid-1990s was the cause of health problems, including cancer. Particular concern was directed at SR-51, a desealant chemical mixture containing the following four solvents: aromatic 150 solvent (Aro150), dimethylacetamide, thiophenol (TP), and triethylphosphate. The present study examined the mutagenic potential of SR-51 using a range of well-known mutagen and genotoxin assays. The tests used were i) a modified version of the Ames test, ii) the mouse lymphoma assay, iii) the comet assay (a single-cell gel electrophoresis assay), and iv) a mouse micronucleus test. The modified Ames test used mixed bacterial strains in liquid suspension media. The Ames test results showed that SR-51 (tested up to the cytotoxic concentration of 36 microg/ml, 30 min incubation) in the presence and absence of S9 metabolic activation was not mutagenic. The mouse lymphoma assay used cultured mouse lymphoma cells in a microwell suspension method. The mouse lymphoma assay was also negative with SR-51 (tested up to the cytotoxic concentration of 22.5 microg/ml, 3 h incubation) in the presence and absence of S9 metabolic activation. The Comet assay, using cultured mouse lymphoma cells, showed no evidence of DNA damage in cells exposed up to the cytotoxic concentration of SR-51 at 11.25 microg/ml. The in-vivo mouse micronucleus test was undertaken in wild-type C57Bl6J male mice dosed orally with SR-51for 14 days with a single daily dose up to 360 mg/kg/day (the maximum-tolerated dose). No increases were observed in micronuclei (MN) frequency in bone marrow collected (24 h after final dose) from SR-51-treated mice compared to the number of MN observed in bone marrow collected from untreated mice. Tissues collected from treated mice at necropsy demonstrated a significant increase in spleen weights in the high dose mice. Gas chromatography analysis of SR-51 identified more than 40 individual components and an oxidation product, diphenyldisulfide derived from TP under conditions of mild heating. In conclusion, there was no evidence that SR-51 is mutagenic.

Fatigue in levodopa-naive subjects with Parkinson disease.

BACKGROUND: Fatigue is a common complaint in Parkinson disease (PD). We investigated fatigue in a cohort of previously untreated patients with early PD enrolled in the Earlier vs Later Levodopa (ELLDOPA) clinical trial. METHODS: A total of 361 patients were enrolled in the randomized, double-blind, placebo-controlled ELLDOPA trial and assigned to receive placebo or carbidopa-levodopa 37.5/150 mg, 75/300 mg, or 150/600 mg daily for 40 weeks, followed by a 2-week medication washout period. Subjects who scored >4 on the Fatigue Severity Scale were classified as fatigued. PD severity was assessed using the Unified Parkinson's Disease Rating Scale (UPDRS), Hoehn-Yahr scale, and Schwab-England Activities of Daily Living Scale. A subgroup of subjects underwent [(123)I]-beta-CIT SPECT to measure striatal dopamine transporter density. RESULTS: Of the 349 ELLDOPA subjects who completed fatigue measures, 128 were classified as fatigued at baseline. The fatigued group was significantly more impaired neurologically (UPDRS, all subscales and Hoehn and Yahr staging) and functionally (Schwab-England Scale) but no significant differences were observed in beta-CIT measurements between the two groups. Analysis of covariance showed a greater increase in fatigue score from baseline to the end of the 2-week washout in the placebo group (0.75 points) than in the three groups receiving levodopa (increases of 0.30 [150 mg/day], 0.36 [300 mg/day], and 0.33 [600 mg/day]; p = 0.03 for heterogeneity). CONCLUSIONS: Fatigue is a frequent symptom in early, untreated, non-depressed patients with Parkinson disease (PD), affecting over 1/3 of the patients in this cohort at baseline and 50% by week 42. Fatigue was associated with the severity of PD, and progressed less in patients treated with levodopa.

Detection of Huntington's disease decades before diagnosis: the Predict-HD study.

OBJECTIVE: The objective of the Predict-HD study is to use genetic, neurobiological and refined clinical markers to understand the early progression of Huntington's disease (HD), prior to the point of traditional diagnosis, in persons with a known gene mutation. Here we estimate the approximate onset and initial course of various measurable aspects of HD relative to the time of eventual diagnosis. METHODS: We studied 438 participants who were positive for the HD gene mutation, but did not yet meet the diagnostic criteria for HD and had no functional decline. Predictability of baseline cognitive, motor, psychiatric and imaging measures was modelled non-linearly using estimated time until diagnosis (based on CAG repeat length and current age) as the predictor. RESULTS: Estimated time to diagnosis was related to most clinical and neuroimaging markers. The patterns of association suggested the commencement of detectable changes one to two decades prior to the predicted time of clinical diagnosis. The patterns were highly robust and consistent, despite the varied types of markers and diverse measurement methodologies. CONCLUSIONS: These findings from the Predict-HD study suggest the approximate time scale of measurable disease development, and suggest candidate disease markers for use in preventive HD trials.

Hyperspectral infrared imaging of HF(v, J) chemiluminescence and gain in chemically reacting flowfields.

This paper presents results from investigations of chemically reacting flowfields and optical gain profiles in HF chemical laser media by infrared hyperspectral imaging. Subsonic and supersonic chemiluminescent F+H2 reacting flowfields, produced in high-fluence microwave-driven reactors, were imaged at a series of wavelengths, 2.6-3.1 microm, by a low-order, spectrally scanning Fabry-Perot interferometer mated to an infrared camera. The resulting hyperspectral data cubes define the spectral and spatial distributions of the emission. Spectrally resolved images at high spatial resolution were processed to determine spatial distributions of the excited-state concentrations of the product HF(v, J) molecules, as well as spatial distributions of small-signal gain on specific laser transitions. Additional high-resolution Fourier transform spectroscopy and spectral fitting analysis determined detailed excited-state distributions in the reacting flowfields. The measurements showed that energetic HF(v, J) state distributions were generated by both the supersonic and fast-flow subsonic mixing schemes. In particular, the subsonic reactor produced a spatially distributed field of inverted, near-nascent state populations, with small-signal gains near 2-3%/cm.

Rasagiline-associated motor improvement in PD occurs without worsening of cognitive and behavioral symptoms.

BACKGROUND: Cognitive and behavioral adverse events (AEs) such as hallucinations, confusion, depression, somnolence and other sleep disorders commonly limit effective management of motor symptoms in PD. Rasagiline (N-propargyl-1(R)-aminoindan) mesylate is a novel, second-generation, selective, irreversible monoamine oxidase type B inhibitor, demonstrated in monotherapy and adjunctive trials to be effective for PD with excellent tolerability. METHODS: The occurrence of cognitive and behavioral AEs and the change from baseline in the Unified Parkinson's Disease Rating Scale (UPDRS) part I mental subscores were reviewed in two multicenter, randomized, placebo-controlled, 26-week trials of rasagiline for early and moderate-to-advanced patients with PD. The UPDRS is a multi-item rating scale specific to PD; part I rates the patient's intellectual impairment, thought disorders, depression and motivation/initiative. RESULTS: The TEMPO study evaluated rasagiline monotherapy in early PD patients (n=404). The PRESTO study evaluated rasagiline as adjunctive therapy in moderate-to-advanced PD patients with motor complications who were receiving optimized levodopa/carbidopa (n=472). In the analysis of adverse event reporting for both studies, no cognitive and behavioral AE in either the rasagiline 1 mg or placebo groups exceeded 10% of the study population and the frequency differences between rasagiline 1 mg and placebo never exceeded 3%. There was no adverse effect on the UPDRS mental subscore relative to placebo in either of the two studies. CONCLUSION: Rasagiline 1 mg once daily improves PD symptoms and motor fluctuations in early and moderate-to-advanced PD patients without causing significant cognitive and behavioral AE or adverse changes in mentation, behavior and mood.

Safety of rasagiline in elderly patients with Parkinson disease.

The authors examined age effects on adverse events from two randomized, controlled trials of rasagiline, comparing younger (younger than 70 years) and older (70 years and older) subjects. Older patients were more prone to serious adverse effects than younger patients, but there was no statistical interaction between age and rasagiline exposure. This absence of an age-rasagiline interaction suggests that rasagiline does not require special safety precautions for elderly subjects with Parkinson disease.

Effects of lipids and lipid-lowering therapy on hemostatic factors in patients with myocardial infarction.

BACKGROUND: The risk of cardiovascular disease (CVD) is associated with specific hemostatic markers and lipid profiles, and evidence indicates that there are associations between lipid profiles and the levels of certain hemostatic factors. The disturbances in hemostasis and the risk of CVD can be ameliorated by lipid-lowering therapy. OBJECTIVE: We investigated the associations of lipid profiles with factor (F)VIIa, von Willebrand factor (VWF), D-dimer and plasminogen activator inhibitor-1 (PAI-1), and examined whether lipid-lowering statin therapy would affect the levels of these hemostatic markers. PATIENTS AND METHODS: This cross-sectional study analyzed 1045 postmyocardial infarction patients. RESULTS: In multivariate regression analyses (without adjusting for clinical covariates) HDL-cholesterol (HDL-C) and HDL size were independent and significant predictors of FVIIa; HDL size was a predictor of VWF; HDL size, HDL-C and LDL size were predictors of D-dimer; and triglyceride and HDL size were predictors of PAI-1. After adjusting for clinical covariates, HDL-C, lipoprotein (Lp)(a), apolipoprotein B (apoB) and warfarin were independent and significant predictors of FVIIa; HDL size, age, diabetes mellitus, insulin, race and warfarin were predictors of VWF; HDL-C, HDL size, LDL size, age, warfarin, hypertension and gender were predictors of D-dimer; and triglyceride, HDL size, body mass index, insulin and hypertension were predictors of PAI-1. Patients on statin therapy had significantly lower levels of D-dimer than those who were not on this therapy. CONCLUSION: There are significant associations of lipid profiles with hemostatic factors, the directions of which suggest novel pathways by which dyslipidemia may contribute to coronary heart disease.

Effects of a desealant formulation, SR-51(®) and its individual components on the oxidative functions of mitochondria.

The Royal Australian Air Force has reported that personnel involved in F-111 fuel tank maintenance were concerned that exposure to a range of chemicals during the period 1977-mid-1990s was the cause of health problems. Particular concern was directed at a desealant chemical mixture known as SR-51(®). The current study, using in vitro submitochondrial assays, was designed to investigate the relative toxicities of the four components of SR-51(®) (Aromatic 150 solvent (Aro150), dimethylacetamide (DMA), thiophenol (TP) and triethylphosphate (TEP)). Based on the EC(50) values, TP and Aro150 were the most toxic components and were markedly more toxic than TEP and DMA.

Assessment of neuroimaging techniques as biomarkers of the progression of Parkinson's disease.

A major goal of research in Parkinson's disease (PD) has been the development of treatments to slow the progressive degeneration of the nigrostriatal dopaminergic system and to reduce the functional decline of patients. Because of the uncertainty in the ability of the clinical evaluation to reflect the status of the nigrostriatal dopaminergic system once dopaminergic therapy has commenced, investigators in PD have sought to develop alternative measures of disease. One approach, which has been extensively explored, is neuroimaging with radiotracers that interact with processes central to dopaminergic neurotransmission in the nigrostriatal dopaminergic axons-conversion of levodopa to dopamine through aromatic amino acid decarboxylase (AADC), [(18)F]fluorodopa PET, storage of dopamine in synaptic vesicles via the vesicular monoamine transporter 2 (VMAT2), (+)-[(11)C]dihydrotetrabenazine PET, and reuptake of dopamine into axons via the dopamine transporter (DAT), [(123)I]beta-CIT SPECT, and a number of other PET and SPECT ligands. During the 54(th) Annual Meeting of the American Academy of Neurology, a group of investigators active in the fields of biomakers, neuroimaging, and neuroprotection met to review the three techniques mentioned above. Prior to the meeting, the participants developed consensus on a set of 10 criteria for a neuroimaging technique to be considered adequate as a biomarker for progression of PD and levels at which the available data for each technique indicate that the criterion was met. The criteria and each of the three imaging techniques mentioned above were reviewed, and the results of that meeting are presented.

Testicular changes induced by chronic exposure to the herbicide formulation, Tordon 75D (2,4-dichlorophenoxyacetic acid and picloram) in rats.

The second most used herbicide in the Vietnam war was Agent White, which contained the active components 2,4-dichlorophenoxyacetic acid (2,4-D) and 4-amino-3,5,6-trichloropicolinic acid (picloram). The herbicide formulation Tordon 75D is similar in terms of its active components to Agent White and is currently used by the agricultural industry in Australia. As part of an investigation into the possible adverse effects of this herbicide on male reproductive performance, groups of five male rats were gavaged 5 days a week for 9 weeks with either 0.125 ml/kg (low dose), 0.25 ml/kg (middle dose), or 0.5 ml/kg (high dose) Tordon 75D or water (controls). The high dose corresponded to 150 mg/kg body weight 2,4-D and 37.5 mg/kg picloram acid equivalents. At the end of the treatment period, the testes were collected, weighed, and examined histologically and blood samples were taken to determine serum testosterone. Groups of high dose animals were also examined after 1, 2, and 4 weeks treatment. The 9 weeks treatment with Tordon 75D caused severe reduction in testicular weight in some high dose animals. Histologically, the small testes showed shrunken tubules with germ cell depletion. This damage was still evident in some rats following a 21 weeks recovery period suggesting that the testicular damage was permanent. Testicular damage was not due to endocrine disruption as there were no significant differences in the serum concentration of testosterone in control animals compared to Tordon 75D-treated animals. Blood levels associated with the high dose were determined in a separate study and were much higher than those likely to be obtained by occupational exposure to this herbicide.

A study of the potential for a herbicide formulation containing 2,4-d and picloram to cause male-mediated developmental toxicity in rats.

Male Vietnam veterans have repeatedly expressed concern that exposure to herbicides in Vietnam may have caused birth defects in their offspring. The second most used herbicide was a mixture of 2,4-D and picloram called Agent White. This study is an investigation into the possible male-mediated reproductive toxicology of this herbicide. Male rats were gavaged for 5 days per week for 9 weeks with a mixture of 2,4-D and picloram called Tordon 75D(R) (the Australian derivative of Agent White). Three doses were tested; the high dose was considered the maximum tolerated dose. Each male was mated with two untreated females during weeks 2 and 3, 4 and 5, and 8 and 9 of treatment, and with four untreated females after an 11-week recovery period. Negative controls were males dosed with distilled water, and positive controls were males dosed with cyclophosphamide at 5.1 mg/kg/day. All mated females were killed on day 20 of gestation, and the fetuses were weighed and examined for either structural malformations or skeletal development. Litter size, fetal weight, and malformation rate were all unaffected by treatment. The cyclophosphamide positive controls showed the expected large increase in postimplantation loss. In general, within the limitations of the power of the study, the results did not show any evidence that exposure to a herbicide formulation containing 2,4-D and picloram is likely to cause male-mediated birth defects or other adverse reproductive outcomes.

[123I]beta-CIT SPECT imaging assessment of the rate of Parkinson's disease progression.

BACKGROUND: [123I]beta-CIT and SPECT imaging of the dopamine transporter is a sensitive biomarker of PD onset and severity. OBJECTIVE: In this study, the authors examine the change in [123I]beta-CIT uptake in sequential SPECT scans to assess the rate of progression of the dopaminergic terminal loss in patients with PD. METHODS: Patients with PD (n = 32) and healthy controls (n = 24) recruited from the Yale Movement Disorders Center underwent repeat [123I]beta-CIT SPECT imaging during a 1- to 4-year period. The primary imaging outcome was the ratio of specific to nondisplaceable striatal activity. Disease severity was assessed by Hoehn and Yahr staging, and Unified Parkinson Disease Rating Scale after 12 hours off drug. RESULTS: Sequential SPECT scans in PD subjects demonstrated a decline in [123I]beta-CIT striatal uptake of approximately 11.2%/year from the baseline scan, compared with 0.8%/year in the healthy controls (p < 0.001). Although [123I]beta-CIT striatal uptake in the PD subjects was correlated with clinical severity, the annual percentage loss of [123I]beta-CIT striatal uptake did not correlate with the annual loss in measures of clinical function. CONCLUSIONS: - The rate of dopaminergic loss in PD is significantly greater than that of healthy controls, and [123I]beta-CIT SPECT imaging provides a quantitative biomarker for the progressive nigrostriatal dopaminergic degeneration in PD. As new protective and restorative therapies for PD are developed, dopamine transporter imaging offers the potential to provide an objective endpoint for these therapeutic trials.

Clozapine for the treatment of drug-induced psychosis in Parkinson's disease: results of the 12 week open label extension in the PSYCLOPS trial.

OBJECTIVE: To report the results of the 12-week, prospective, open label extension of the 4-week, multicenter, placebo-controlled, double-blind PSYCLOPS (PSYchosis and CLOzapine in the treatment of Parkinsonism) trial. This extension examined the chronic safety and efficacy of clozapine in the treatment of drug-induced psychosis in Parkinson's disease (PD). BACKGROUND: Psychosis is a serious late complication of PD and may be a harbinger to increased mortality. Clozapine, the first atypical antipsychotic, was shown in several small open label studies to improve psychosis without worsening of motor symptoms. This was recently confirmed in the double-blind PSYCLOPS trial. METHODS: The 53 patients who completed the double-blind portion of PSYCLOPS were evaluated on their original randomized treatment (clozapine or placebo), then had study medication stopped. All were started on clozapine. The patients from both treatment groups were evaluated every 4 weeks over a 12-week period using standardized measures for psychosis and PD. RESULTS: The mean dose of clozapine was 28.78 mg/day. Those originally treated with placebo improved significantly in Brief Psychiatric Rating Scale and clinical global scores for psychosis to the same degree as the group originally randomized to clozapine in the double-blind study. Both groups maintained their response to week 16 (end of the combined double-blind and open label portions). There was no worsening of motor features as measured by the Unified Parkinson's disease rating scale. Eighteen patients were either hospitalized or died during the trial. The most common reasons were pulmonary. CONCLUSIONS: Low-dose clozapine is effective in treating drug-induced psychosis without worsening motor features of PD, and the response is maintained for at least 4 months. Patients with psychosis and PD were previously described as a group with high risk for morbidity and mortality. The high risk continues despite antipsychotic therapy.

The productivity and impact of the Leukemia & Lymphoma Society Scholar Program: the apparent positive effect of peer review.

A study was conducted to compare the "productivity" of a cohort of research grant applicants selected by peer review to be scholars of The Leukemia Society of America (now The Leukemia & Lymphoma Society) with a matched cohort of applicants not so selected during the period 1981 to 1990. One hundred and twenty-four scholars and 124 nonfunded applicants were studied. Two bibliometric variables and their derivatives were examined from the Institute of Scientific Information database: the number of papers published and the number of citations to those papers. Published papers were measured through December 31, 1999, and citation counts to these papers through December 31, 2000. Scholars published 10,301 papers through the period of observation and nonfunded applicants published 6442 papers. Scholars' papers were cited 536,283 [corrected] times, whereas nonfunded applicants' papers were cited 245,586 times. The mean citations per paper were 52 for scholars and 38 for nonfunded applicants. The papers published per scholar, citations per scholar, and citations per paper per scholar were significantly greater than the corresponding measures for nonfunded applicants (P < 0.0001 in each case). Scholar's papers were cited 30% more often, whereas nonfunded applicants were cited 10% more frequently, than a comparison group of scientists publishing in the same journal in the same year. High-impact papers, e.g., papers that were cited more than 200 times, were nearly three times as frequent among scholars (494 papers) as among nonfunded applicants (173 papers). This difference was highly significant. The good (better than baseline) performance of nonfunded applicants may be a reflection of self-selection among the applicant pool for this competitive award; the more productive performance of the scholars is probably the result of the selection decisions made during the peer-review process.

The in vitro evaluation of the toxicities of three related herbicide formulations containing ester derivatives of 2,4,5-T and 2,4-D using sub-mitochondrial particles.

The aim of this investigation was to determine the contribution made by the different components of herbicide formulations to the overall toxicity of the formulations. Three related herbicide formulations were chosen. The first, Agent Orange, consisted only of the butyl esters of 2,4,5-T and 2,4-D. The second was Agent Orange diluted with diesel fuel and the third formulation tested was a tree and blackberry killer, which consisted of the butyl ester of 2,4,5-T, the ethyl ester of 2,4-D, diesel fuel and two surfactants. The potential toxic effects of these three formulations were evaluated by determining their inhibitory effects on the oxidative functions of submitochondrial particles prepared from beef heart mitochondria. The effective concentration that caused a 50% inhibition of the activities of the submitochondrial particles was determined for all three formulations. When the toxicity of the individual components of these formulations was evaluated, it was established that the so-called 'inert' components i.e. diesel fuel and surfactants contributed approximately 50% of the overall toxicity of the complete formulations. Hence the results confirm the importance of evaluating the toxicity of complete formulations, rather than only focussing on the active components. While cellular and sub-cellular assays cannot account for pharmacokinetic and pharmacodynamic changes that may affect the toxicity of xenobiotics, the sub-mitochondrial particle test is useful as an initial screening assay.