Development of a dual MCP framing camera for high energy x-rays.

Recently developed diagnostic techniques at LLNL require recording backlit images of extremely dense imploded plasmas using hard x-rays, and demand the detector to be sensitive to photons with energies higher than 50 keV [R. Tommasini et al., Phys. Phys. Plasmas 18, 056309 (2011); G. N. Hall et al., "AXIS: An instrument for imaging Compton radiographs using ARC on the NIF," Rev. Sci. Instrum. (these proceedings)]. To increase the sensitivity in the high energy region, we propose to use a combination of two MCPs. The first MCP is operated in a low gain regime and works as a thick photocathode, and the second MCP works as a high gain electron multiplier. We tested the concept of this dual MCP configuration and succeeded in obtaining a detective quantum efficiency of 4.5% for 59 keV x-rays, 3 times larger than with a single plate of the thickness typically used in NIF framing cameras.

AXIS: an instrument for imaging Compton radiographs using the Advanced Radiography Capability on the NIF.

Compton radiography is an important diagnostic for Inertial Confinement Fusion (ICF), as it provides a means to measure the density and asymmetries of the DT fuel in an ICF capsule near the time of peak compression. The AXIS instrument (ARC (Advanced Radiography Capability) X-ray Imaging System) is a gated detector in development for the National Ignition Facility (NIF), and will initially be capable of recording two Compton radiographs during a single NIF shot. The principal reason for the development of AXIS is the requirement for significantly improved detection quantum efficiency (DQE) at high x-ray energies. AXIS will be the detector for Compton radiography driven by the ARC laser, which will be used to produce Bremsstrahlung X-ray backlighter sources over the range of 50 keV-200 keV for this purpose. It is expected that AXIS will be capable of recording these high-energy x-rays with a DQE several times greater than other X-ray cameras at NIF, as well as providing a much larger field of view of the imploded capsule. AXIS will therefore provide an image with larger signal-to-noise that will allow the density and distribution of the compressed DT fuel to be measured with significantly greater accuracy as ICF experiments are tuned for ignition.

[Depressive syndrome and ischemic cardiopathy]. / Sindrome depressiva e cardiopatia ischemica.

The prevalence of ischemic heart disease and depressive syndrome in the occidental population is high. Clinical depression appears to be an independent risk factor for coronary heart disease. Depression after an acute coronary event exerts a profoundly negative effect on quality of life and is related to poor prognosis (increased mortality rates and further cardiac events). Moreover, medical therapy in patients with ischemic heart disease and depressive symptoms is not free of problems. The purpose of this review is to present the relationships between depression and cardiovascular disease on the data collected from different studies and make recommendations for improving assessment and treatment of depressive symptoms in the family practice, internal medicine or cardiologist setting. Only an interdisciplinary integration among basic scientists and clinicians, will decrease the comorbidity.

[Statins: from hypocholesteremic drugs to antiatherogenic agents]. / Statine: da farmaci ipocolesterolemizzanti ad agenti antiaterogeni.

Statins (3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors) are widely used for the treatment of hypercholesterolemia. They reduce LDL levels more than other lipid-lowering drugs. Moreover, they are effective in raising HDL and even in reducing triglyceride levels. Statins have an excellent tolerability and safety. Clinical trials in patients with and without ischemic heart disease and with and without high cholesterol levels have demonstrated that statins significantly reduce the relative risk of major coronary events and of total mortality. Other mechanisms independent of LDL lowering may play an important role in the clinical benefits conferred by these drugs and may broaden their therapeutic indications from lipid-lowering to antiatherogenic agents.

[Platelet glycoprotein IIB-IIIA receptor inhibitors in patients with ischemic heart disease]. / Gli inibitori dei recettori glicoproteici IIB-IIIA delle piastrine nei pazienti con cardiopatia ischemica.

Glycoprotein IIb-IIIa receptor inhibitors are the newest anti-platelets drugs currently used in patients with coronary artery disease. We examined mechanisms of their action and different pharmacokinetic and pharmacodynamic characteristics of the four glycoprotein IIb-IIIa antagonists evaluated in randomized, controlled and multicenter trials. We reviewed results of these trials in the settings of percutaneous revascularizations procedures or unstable coronary syndromes. Platelet glycoprotein IIb-IIIa receptor inhibitors reduced incidence of cardiac death and myocardial infarction during the short- and midterm, and benefit was greater in: a) patients undergoing coronary angioplasty with or without stent implantation, particularly in the presence of unstable angina, diabetes or complex and diffuse coronary artery disease; b) as a direct therapy of unstable coronary syndromes, particularly in patients with refractory angina, diabetes and elevated Troponin; more recently they have been used as adjuvant therapy in acute myocardial infarction. Infusion of these drugs was not associated with higher rates of major bleedings.

Dopamine D2 receptor gene polymorphism and the risk of levodopa-induced dyskinesias in PD.

OBJECTIVE: To investigate whether polymorphisms in the genes for dopamine receptors D1 and D2 are associated with the risk of developing peak-dose dyskinesias in PD. BACKGROUND: Peak-dose dyskinesias are the most common side effects of levodopa therapy for PD. The identified predictors may only partially account for the risk of developing peak-dose dyskinesias because a substantial proportion of patients never develop peak-dose dyskinesias. Genetic factors could play a role in determining the occurrence of peak-dose dyskinesias. METHODS: A case-control study of 136 subjects with sporadic PD and 224 population control subjects. We studied three polymorphisms involving the dopamine receptor D1 gene and one intronic short tandem repeat polymorphism of the dopamine receptor D2 gene. RESULTS: The polymorphisms of the dopamine receptor D1 gene were not associated with the risk of developing PD or peak-dose dyskinesias. The 15 allele of the polymorphism of the dopamine receptor D2 gene was more frequent in parkinsonian subjects than in control subjects. More important, the frequency of both the 13 allele and the 14 allele of the dopamine receptor D2 gene polymorphism was higher in nondyskinetic than in the dyskinetic PD subjects. The risk reduction of developing peak-dose dyskinesias for PD subjects carrying at least 1 of the 13 or 14 alleles was 72% with respect to the PD subjects who did not carry these alleles. CONCLUSIONS: Certain alleles of the short tandem repeat polymorphism of the dopamine receptor D2 gene reduce the risk of developing peak-dose dyskinesias and could contribute to varying susceptibility to develop peak-dose dyskinesias during levodopa therapy.

Loss of long-duration response to levodopa over time in PD: implications for wearing-off.

OBJECTIVE: To determine the modifications of the long-duration response to levodopa in PD over a 1-year period. BACKGROUND: The development of predictable motor fluctuations in PD has been attributed mainly to modifications over time of the short-duration response to levodopa, whereas the role of the long-duration response has not been widely investigated. METHODS: In 17 patients with PD the authors examined prospectively both the short-duration response and the long-duration response to levodopa under standardized conditions on two different occasions separated by a period of approximately 1 year (11.7 +/- 3.6 months). RESULTS: At the end of the follow-up period, the short-duration response increased in magnitude but did not change significantly in duration. A total of 24% of patients lost the long-duration response 1 year after their first examination, but a sustained long-duration response could be reestablished by shortening the interdose interval for levodopa intake. Moreover, the duration of the long-duration response after discontinuation of treatment became significantly shorter during 1 year. CONCLUSION: Modifications of the long-duration response may have a pivotal role in generating a fluctuating response, and suggest that therapeutic strategies based on maintenance of the long-duration response should be sought to avoid the appearance of motor fluctuations.

CAG repeat length and clinical features in three Italian families with spinocerebellar ataxia type 2 (SCA2): early impairment of Wisconsin Card Sorting Test and saccade velocity.

We report on the clinical, neuropsychological, neurophysiological, computerized eye movement, magnetic resonance imaging (MRI) and molecular findings from 17 individuals affected with spinocerebellar ataxia type 2 (SCA2) belonging to three families. The average age at onset of the symptoms was 35.6, 11.9 (mean, SD) years. The mean age at onset of the symptoms in the parents was 44.8, 8.2 years, and in the offspring it was 28.7, 7.2 years. In 12 parent-child pairs, the mean anticipation was -15.75, 9.1 years (range -8.1 to -23.3 years, t = -4.9, P = < 0.002). The mutated SCA2 alleles ranged from 38 to 42 CAG repeats, while the normal alleles ranged from 22 to 24 repeats, with 97% of the alleles having 22 repeats. Small differences in the number of CAG repeats influenced the age at onset and rate of progression of the disease considerably. Indeed, patients presenting with their first symptom at an age of 35 years or later with a slower course of the disease harboured between 38 and 39 repeats. In contrast, patients carrying > or = 40 CAG repeats manifested the disease prior to 30 years of age and had a faster disease progression toward incapacity. The presenting symptom was always gait ataxia. Slow saccades occured from the beginning of the disease despite normal delay, accuracy and smooth pursuit eye movements. The neuropsychological study showed early and selective impairment of conceptual reasoning ability, as detected by the Wisconsin Card Sorting Test (WCST). It is noteworthy that a significant mutual relationship was observed between performance on the WCST and saccade velocity. All of these findings favour the hypothesis that the disease process of SCA2 in regions other than the cerebellum and brain stem affects severely and early those cortical structures involved in the control of both visually guided saccades and WCST performance.

Long-duration response to levodopa influences the pharmacodynamics of short-duration response in Parkinson's disease.

The long-duration response (LDR) to chronic levodopa treatment may mask the short-duration response (SDR) to a single dose of the drug in Parkinson's disease (PD). As a result, the measurement of SDR may be inaccurate for establishing levodopa dosing regimen in individual patients. To evaluate the possible contamination of SDR by LDR, we investigated in 16 patients with PD the characteristics of SDR to a single dose of levodopa administered after a prolonged washout from chronic therapy and after a 15-day treatment period with levodopa. Levodopa treatment produced a sustained LDR, and the SDR, measured on the 15th day of treatment, had lower magnitude and shorter duration than the response recorded after washout. Moreover, after treatment, SDR did not vary between patients with mild and severe PD, whereas, after washout, severely affected patients had larger but shorter SDR than mildly affected patients. The evaluation of SDR without the interference of LDR is critical in defining the characteristics of the therapeutic response to levodopa.

Short-term levodopa test assessed by movement time accurately predicts dopaminergic responsiveness in Parkinson's disease.

Short-term challenges with dopaminergic agents are used in patients with idiopathic Parkinson's disease (PD) to predict the therapeutic effect of sustained levodopa treatment, but false-negative results often occur. We prospectively evaluated 74 patients with clinically diagnosed IPD and compared the predictive value of a short-term levodopa test assessed by movement time (MT) with the predictive value obtained by the evaluation with the motor examination part of the Unified Parkinson's Disease Rating Scale (UPDRS-ME). The response to long-term levodopa was accurately predicted in 96% of patients by assessing the response to the short-term test with MT and in 80% of cases with UPDRS-ME. Similar predictive values were obtained by separately analyzing 21 de novo patients. The short-term test also accurately predicted the magnitude of improvement with long-term treatment. We conclude that the predictive value for long-term dopaminergic responsiveness may be further enhanced by evaluating the short-term pharmacologic challenges with MT analysis. This is particularly useful to select de novo patients for drug trials with dopaminergic agents.

The subacute levodopa test for evaluating long-duration response in Parkinson's disease.

The clinical relevance of a long-duration response (LDR) to levodopa therapy in Parkinson's disease (PD) has not been widely recognized. In 25 patients with moderate PD, we measured LDR on motor function after short periods of treatment with levodopa (subacute tests). Each subacute test lasted 15 days and consisted of the oral administration of levodopa at various interdose intervals (IDIs) of 48, 24, 12, 8, 6, and 5 hours. The goal for a subacute test was to achieve a satisfactory antiparkinsonian effect before the last levodopa dose (day 15), i.e., an LDR greater than 50% of the maximal response following an acute levodopa test (LDR-endpoint). Twenty-one patients (84%) reached the LDR-endpoint. The IDI at which levodopa was administered clearly differentiated patients who were otherwise clinically indistinguishable when evaluated at baseline off medication or after an acute levodopa test. The IDI schedule that produced a satisfactory LDR was specific for each patient, since longer DIs failed to produce the required LDR, and a shorter IDI schedule (resulting in larger cumulative dosage of levodopa) did not significantly enhance the response. Also, the LDR decay rate after discontinuation of treatment was individual for each patient and independent of the cumulative amount of levodopa administered. Both the IDI schedule and the LDR decay rate may reflect the ability of nigrostriatal neurons to store and to release dopamine formed from the exogenous precursor. The assessment of the LDR to levodopa by subacute tests is useful for establishing the appropriate dose of the drug, as well as for developing levodopa sparing strategies in PD patients.

Usefulness of movement time in the assessment of Parkinson's disease.

Reaction time (RT) and movement time (MT) are reported to be delayed in Parkinson's disease (PD), but their clinical utility and relationship with clinical findings is still uncertain. We investigated RT and MT in 22 PD patients at baseline conditions and following acute oral trials of levodopa and biperiden, an anticholinergic drug. At baseline conditions, RT and MT of PD patients were abnormally delayed compared with those of 16 normal control subjects. Both RT and MT were longer in more severely affected patients compared with the mild PD patients; in the mild PD patients with asymmetrical signs both responses were longer on the more affected side. Bradykinesia was the clinical symptom that best correlated with the objective measurements, with a stronger correlation for MT than for RT. The oral administration of levodopa significantly improved both the responses, whereas biperiden was ineffective. The magnitude of RT and MT improvement after levodopa differed; MT improvement was related to PD severity, whereas RT improvement was not. These results suggest that MT, rather than RT, is an objective, simple, and reliable tool to evaluate bradykinesia and its levodopa-induced modifications in PD.