Genetic susceptibility to environmental toxicants in ALS

Amyotrophic lateral sclerosis (ALS): three letters that change the people's life. For ever

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease affecting the motor nervous system. It causes progressive and cumulative physical disabilities in patients, and leads to eventual death due to respiratory muscle failure. The disease is diverse in its presentation, course, and progression. We do not yet fully understand the cause or causes of the disease, nor the mechanisms for its progression; thus, we lack effective means for treating this disease. Currently, we rely on a multidisciplinary approach to symptomatically manage and care for patients who have ALS. Although amyotrophic lateral sclerosis and its variants are readily recognized by neurologists, about 10% of patients are misdiagnosed, and delays in diagnosis are common. Prompt diagnosis, sensitive communication of the diagnosis, the involvement of the patient and their family, and a positive care plan are prerequisites for good clinical management. A multidisciplinary, palliative approach can prolong survival and maintain quality of life. Treatment with Riluzole improves survival but has a marginal effect on the rate of functional deterioration, whereas non-invasive ventilation prolongs survival and improves or maintains quality of life. In this Review, we discuss the diagnosis, management, and how to cope with impaired function and end of life on the basis of our experience, the opinions of experts, existing guidelines, and clinical trials. Multiple problems require a multidisciplinary approach including aggressive symptomatic management, rehabilitation to maintain motor function, nutritional support (enteric feeding, gastrostomy), respiratory support (non invasive home ventilation, invasive ventilation, tracheotomy), augmentative communication devices, palliative care, psychological support for both patients and families (because family members so often play a central role in management and care), communication between the care team, the patient and his or her family, and recognition of the clinical and social effects of cognitive impairment. Social, bioethical, and financial issues as well as advance directives should be addressed. A plethora of evidence-based guidelines should be compiled into an internationally agreed guideline of best practice. The multidisciplinary team has changed the history of disease, with still no curative therapy available.

Genetic and life-history trait variation of the amphipod Melita plumulosa from polluted and unpolluted waterways in eastern Australia

To monitor genetic diversity and environmental contamination in eastern Australia, toxicity studies have employed the sensitive benthic amphipod Melita plumulosa. The goal of this study was to examine the genetic and life-history variability of natural populations of M. plumulosa from the Parramatta (polluted) and Hawkesbury (unpolluted) Rivers. The underlying genetics of the populations in these distinct waterways was examined at one mitochondrial (cytochrome c oxidase subunit I (COI)) and one nuclear (ribosomal internal transcribed spacer region 1 (ITS1)) locus. Seven unique haplotypes for COI were found amongst animals from the Parramatta River, while animals from the Hawkesbury River showed a complete absence of genetic variation at this locus. At ITS1 a total of two sequence variants were found amongst Parramatta River amphipods and three sequence variants among Hawkesbury River animals, with no common variants across the two river systems. To establish whether genetic differences were associated with organismal responses to toxicant exposure, two life-history trait variables (female head length as an estimator of amphipod size and female fecundity) were analyzed. Life-history trait analyses showed that females from the Hawkesbury River were significantly larger and more fecund. These data have critical implications for toxicity tests, the use of laboratory cultures for testing purposes, and environmental contamination in Sydney Harbor.

Environmental epidemiology of essential tremor

BACKGROUND

Essential tremor (ET) is one of the most common neurological disorders. Despite this, the disease mechanisms and etiology are not well understood. While susceptibility genotypes undoubtedly underlie many ET cases, no ET genes have been identified thus far. As with many other progressive, degenerative neurological disorders, it is likely that environmental factors contribute to the etiology of ET. Environmental epidemiology is the study in specific populations or communities of the effect on human health of physical, biologic and chemical factors in the external environment. The purpose of this article is to review current knowledge with regards to the environmental epidemiology of ET.

RESULTS

As will be discussed, a series of preliminary case-control studies in recent years has begun to explore several candidate toxins/exposures, including harmane (1-methyl-9H-pyrido[3,4-b]indole), lead and agricultural exposures/pesticides.

CONCLUSIONS

While several initial results are promising, as will be discussed, additional studies are needed to more definitively establish whether these exposures are associated with ET and if they are of etiological importance.

Elevated blood harmane (1-methyl-9H-pyrido[3,4-b]indole) concentrations in essential tremor

Essential tremor (ET) is a widespread late-life neurological disease. Genetic and environmental factors likely play an etiological role. Harmane (1-methyl-9H-pyrido[3,4-b]indole) is a potent tremor-producing neurotoxin. In 2002, we demonstrated elevated blood harmane concentrations in an initial sample of 100 ET cases compared to 100 controls. Between 2002 and 2007, we assembled a new and larger sample of ET cases and controls. We now attempt to replicate our previous findings. Cases and controls were frequency-matched on age, gender, and race. Blood harmane concentrations were quantified by high-performance liquid chromatography. Subjects comprised 150 ET cases and 135 controls (mean age 65.3+/-15.5 vs. 65.5+/-14.2 years, p=0.94). Mean log blood harmane concentration was approximately 50% higher in cases than controls (0.50+/-0.54g(-10)/ml vs. 0.35+/-0.62g(-10)/ml, p=0.038). In a logistic regression analysis, log blood harmane concentration was associated with ET (OR(adjusted) 1.56, 95% CI 1.01-2.42, p=0.04), and odds of ET was 1.90 (95% CI 1.07-3.39, p=0.029) in the highest versus lowest log blood harmane tertile. Log blood harmane was highest in ET cases with familial ET (0.53+/-0.57g(-10)/ml), intermediate in cases with sporadic ET (0.43+/-0.45g(-10)/ml) and lowest in controls (0.35+/-0.62g(-10)/ml) (test for trend, p=0.026). Blood harmane appears to be elevated in ET. The higher concentrations in familial ET suggests that the mechanism may involve genetic factors.

An epidemiologic investigation of amyotrophic lateral sclerosis in Jefferson County, Missouri, 1998-2002

Amyotrophic lateral sclerosis (ALS) cases diagnosed between 1998 and 2002 were identified to study ALS prevalence and spatial clustering in Jefferson County, Missouri, where an active lead smelter is located. The study used the El Escorial criteria for ALS diagnosis, the capture-recapture analysis for ALS case ascertainment, and the spatial scan statistic for cluster analysis. The estimated crude prevalence of ALS in Jefferson County was 3.9 per 100,000 population (95% CI, 1.7-7.7) at the time point on December 31, 2002. After age-adjustment to the 2002 U.S. population, the prevalence was 4.2 per 100,000 (95% CI, 1.9-6.6). This prevalence estimate was comparable to recent prevalence estimates from Western Europe. A small but significant cluster (p=0.04) was detected around the smelter area. An ALS registry utilizing outpatient, inpatient, and death certificate data is needed to provide comprehensive information for ALS case ascertainment. Etiologic studies are needed to assess whether living in proximity to a lead smelter is associated with the development of ALS.