Biomedical subjects

Brad A Racette

Publications and source records attributed to Brad A Racette.

12 recordsLinked to original sources

PubMed2006

The impact of litigation on neurologic research.

Environmental factors likely contribute to the etiology of many progressive neurologic diseases. Such factors include putative neurotoxins that are often byproducts of commercial industries, potentially exposing corporations to liabilities when their products or activities are linked to the development of disease. Any hint of scientific data that support such a cause and effect relationship often encourages plaintiffs' attorneys to file suits against corporations alleging harm to their clients forcing corporations and employers to defend themselves. Both plaintiff and defendant teams hire expert witnesses who are frequently active investigators in relevant fields to bolster their positions. These legal proceedings can influence investigators and hamper research. Interactions with researchers can lead to personal financial or career gain that may bias research findings or impugn other investigators. Even researchers who have not been retained by either side of a legal dispute may be forced to respond to subpoenas for research data causing a substantial loss of research time for investigators and financial burdens on universities. Courts may require release of research records containing personal health information that could sully the trust research participants have in investigators. Litigation and its peripheral effects may bias investigators, impede research efforts, and harm research participants, thereby undermining efforts to understand the cause of neurologic disease.

Biomedical Research↗

PubMed2006

The use of botulinum toxin therapy for lower-extremity spasticity in children with cerebral palsy.

Hypertonicity is a leading cause of disability for children with cerebral palsy (CP). Botulinum toxin A (BTA) chemically denervates muscle tissue and is commonly used in the management of lower-extremity hypertonicity in children with CP because of its focal effects and wide safety margin. Randomized controlled trials have demonstrated that BTA injections in the ankle flexors, hamstrings, and adductors reduce spasticity and result in improved passive and active range of motion. In other studies, improvements in gait and measurements of functional outcome were found in appropriately selected children who had been injected with BTA. A multidisciplinary treatment approach that includes physical therapists, occupational therapists, orthotists, neurologists, physicians with expertise in performing botulinum toxin injections, orthopedic surgeons, and neurosurgeons is critical to optimize care in children with lower-extremity tone due to CP. In this paper, the authors propose treatment algorithms based on clinical presentation, detailed dosing, and technical information to optimize the treatment of these children. With a multidisciplinary approach, children with lower-extremity hypertonicity due to CP can experience improvements in muscle tone and function.

Algorithms↗

PubMed2006

[18F]FDOPA PET as an endophenotype for Parkinson's Disease linkage studies.

Parkinson disease (PD) is a late onset disorder with age-dependent penetrance that may confound genetic studies, since affected individuals may not demonstrate clinical manifestations at the time of evaluation. The use of endophenotypes, biologic surrogates for clinical disease diagnoses, may permit more accurate classification of at-risk subjects. Positron emission tomography (PET) measurements of 6-[18F]fluorodopa ([18F]FDOPA) uptake indicate nigrostriatal neuronal integrity and may provide a useful endophenotype for PD linkage studies. We performed [18F]FDOPA PET in 11 members of a large, multi-incident Amish family with PD, 24 normals and 48 people with clinically definite idiopathic PD (PD controls). Clinical diagnoses in the Amish were clinically definite PD in four, clinically probable in one, clinically possible in five, and normal in one. Abnormal [18F]FDOPA posterior putamen uptake was defined as less than 3 standard deviations below the normal mean. The criteria were applied to the Amish sample to determine a PET endophenotype for each. We performed genetic simulations using SLINK to model the effect phenoconversion with the PET endophenotype had on logarithm of odds (LOD) scores. PET endophenotype confirmed the status of two clinically definite subjects. Two clinically definite Amish PD subjects had normal PETs. Two possible PD were converted to "PET definite PD." The remainder had normal PETs. The average maximum LOD score with the pre-PET was 6.14 +/- 0.84. Simulating phenoconversion of subjects with unknown phenotypes increased the LOD score to 7.36 +/- 1.23. The [18F]FDOPA PET endophenotype permits phenoconversion in multi-incident PD families and may increase LOD score accuracy and power of an informative pedigree.

Adult↗

PubMed2006

A rapid method for mass screening for parkinsonism.

Epidemiology studies of parkinsonism employ a variety of techniques for unbiased sampling of populations. No current method permits mass screening of all subjects in a population for parkinsonism by movement disorders specialists. We developed and piloted a new approach to facilitate accurate and efficient screening of large populations for diagnosis of parkinsonism and provide data on sensitivity and specificity. We evaluated 2081 welders referred for medical-legal screening. Subjects were video taped using a standardized protocol, and videos were rated on the Unified Parkinson's Disease Rating Scale motor subsection 3 (UPDRS3). A "video rater" viewed video tapes and entered ratings through a web-based database. An "in-person" examiner performed a UPDRS3 examination in a randomly selected subgroup of 48 workers drawn from the 2081. We developed quantitative diagnostic criteria for parkinsonism that established minimum diagnostic thresholds based upon UPDRS3 scores and compared these criteria with diagnosis by an in-person examiner. Specificity of these criteria compared to in-person examination was 91-100% but sensitivity was 56%. A threshold UPDRS3 score greater than nine provided 100% sensitivity and 81% specificity. Liberal criteria identified 266 (13.1%) subjects with probable parkinsonism and 220 (10.8%) subjects with definite parkinsonism. Conservative criteria identified 260 (12.8%) with probable parkinsonism and 122 (6%) with definite parkinsonism. Our screening method permits rapid assessment of parkinsonian signs. An absolute UPDRS3 score greater than nine provided the best combination of sensitivity and specificity for the diagnosis of parkinsonism, while quantitative exam-based criteria for cardinal parkinsonian signs maximized specificity. Parkinsonism as diagnosed by our criteria was common in this group of welders.

Female↗

PubMed2006

Influence of heterozygosity for parkin mutation on onset age in familial Parkinson disease: the GenePD study.

BACKGROUND: The PARK2 gene at 6q26 encodes parkin, whose inactivation is implicated in an early-onset autosomal recessive form of Parkinson disease (PD). OBJECTIVE: To evaluate the influence of heterozygosity for parkin mutation on onset age in a sample of families with at least 2 PD-affected members. DESIGN: Clinical and genetic study. SETTING: Twenty collaborative clinical sites. PATIENTS: Patients with familial PD collected in the GenePD study. Studied families were selected for (1) affected sibling pairs sharing 2 alleles identical by state at PARK2 (D6S305) or (2) 1 or more family members with onset age younger than 54 years, regardless of D6S305 status. At least 1 member from each of 183 families underwent comprehensive screening for deletion/insertion variants and point mutations in PARK2. MAIN OUTCOME MEASURES: Mutations in the parkin gene were screened by means of single-stranded conformation polymorphism and sequencing in all 12 coding exons and flanking intronic sequences for point mutations and duplex quantitative polymerase chain reaction in all exons for rearrangement, duplication, and deletion. RESULTS: Mutations were found in 23 families (12.6% of those screened). Among the mutation-positive families, 10 (43%) contained compound heterozygotes; 3 (13%), homozygotes; and 10 (43%), heterozygotes. The onset age in patients with parkin gene mutations ranged from 20 to 76 years. Patients with 1 parkin mutation had an 11.7-year age at onset than did patients with none (P = .04), and patients with 2 or more parkin mutations had a 13.2-year decrease in age at onset compared with patients with 1 mutation (P = .04). CONCLUSIONS: These data indicate that parkin mutations are not rare in multiply affected sibships, and that heterozygous mutation carrier status in PARK2 significantly influences age at onset of PD.

Adult↗

PubMed2005

[18F]FDOPA PET and clinical features in parkinsonism due to manganism.

Manganese exposure reportedly causes a clinically and pathophysiologically distinct syndrome from idiopathic Parkinson's disease (PD). We describe the clinical features and results of positron emission tomography with 6-[18F]fluorodopa ([18F]FDOPA PET) of a patient with parkinsonism occurring in the setting of elevated blood manganese. The patient developed parkinsonism associated with elevated serum manganese from hepatic dysfunction. [18F]FDOPA PET demonstrated relatively symmetric and severely reduced [18F]FDOPA levels in the posterior putamen compared to controls. The globus pallidum interna had increased signal on T1-weighted magnetic resonance imaging (MRI) images. We conclude that elevated manganese exposure may be associated with reduced striatal [18F]FDOPA uptake, and MRI may reveal selective abnormality within the internal segment of the pallidum. This case suggests that the clinical and pathophysiological features of manganese-associated parkinsonism may overlap with that of PD.

Adult↗

PubMed2004

Levodopa with carbidopa diminishes glycogen concentration, glycogen synthase activity, and insulin-stimulated glucose transport in rat skeletal muscle.

We hypothesized that levodopa with carbidopa, a common therapy for patients with Parkinson's disease, might contribute to the high prevalence of insulin resistance reported in patients with Parkinson's disease. We examined the effects of levodopa-carbidopa on glycogen concentration, glycogen synthase activity, and insulin-stimulated glucose transport in skeletal muscle, the predominant insulin-responsive tissue. In isolated muscle, levodopa-carbidopa completely prevented insulin-stimulated glycogen accumulation and glucose transport. The levodopa-carbidopa effects were blocked by propranolol, a beta-adrenergic antagonist. Levodopa-carbidopa also inhibited the insulin-stimulated increase in glycogen synthase activity, whereas propranolol attenuated this effect. Insulin-stimulated tyrosine phosphorylation of insulin receptor substrate (IRS)-1 was reduced by levodopa-carbidopa, although Akt phosphorylation was unaffected by levodopa-carbidopa. A single in vivo dose of levodopa-carbidopa increased skeletal muscle cAMP concentrations, diminished glycogen synthase activity, and reduced tyrosine phosphorylation of IRS-1. A separate set of rats was treated intragastrically twice daily for 4 wk with levodopa-carbidopa. After 4 wk of treatment, oral glucose tolerance was reduced in rats treated with drugs compared with control animals. Muscles from drug-treated rats contained at least 15% less glycogen and approximately 50% lower glycogen synthase activity compared with muscles from control rats. The data demonstrate beta-adrenergic-dependent inhibition of insulin action by levodopa-carbidopa and suggest that unrecognized insulin resistance may exist in chronically treated patients with Parkinson's disease.

Animals↗

PubMed2004

Novel haplotypes in 17q21 are associated with progressive supranuclear palsy.

Progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD) are sporadic neurodegenerative diseases presenting as atypical parkinsonian disorders, characterized by the presence of tau-positive neurofibrillary tangles. Recently, an extended haplotype (H1E) of 787.6 kb that comprises several genes including MAPT showed increased association with PSP. The objective of this study was to determine the size of the H1E haplotype associated with PSP and CBD in different populations and to identify specific subhaplotypes in the background of H1E haplotype. Nineteen single nucleotide polymorphisms (SNPs) in the 17q21 region were genotyped in two case-control samples. The SNPs that were associated with higher risk for the disease in the homozygous state delimit a region of more that 1 Mb. Haplotype analyses in the Spanish sample showed that the most frequent haplotype found among the patients (H1E'), which extends 1.04 Mb and contains several genes such as MAPT, CRHR1, IMP5, Saitohin, WTN3, and NSF. A specific subhaplotype (H1E'A) was present in 16% of PSP patients but was not observed in the controls. Furthermore, the H2E'A haplotype, was rarely present in the disease group suggesting that it plays a protective role. The identification of these specific subhaplotypes that modify risk for PSP/CBD supports the hypothesis that a pathogenic allele exists in a subgroup of PSP patients.

Adult↗

PubMed2003

Botulinum toxin B reduces sialorrhea in parkinsonism.

We report on our open-label experience with botulinum toxin B for the treatment of severe sialorrhea associated with parkinsonism. Nine adult patients with parkinsonism and medically intractable sialorrhea were treated with botulinum toxin B (1,000 units into each parotid gland using superficial landmarks). After treatment, patients experienced a 61% mean subjective improvement and a 42% mean reduction of quantitative saliva production. There were no adverse effects seen in any subjects. Mean peak benefit from injections lasted 14 weeks. We conclude that denervation of salivary glands with botulinum toxin B produces excellent reduction of excessive salivation associated with parkinsonism.

Aged↗

PubMed2003

Dystonia in a patient with ring chromosome 21.

Dystonia associated with chromosomal abnormalities is typically attributed to chromosomal deletions. We describe a patient with ring chromosome 21, with karyotype 46XX,r(21)(p11.2q22.3); 46,XX,dic r(21)(p11.2q22.3); 45, XX, -21, who developed childhood onset cervical dystonia.

Abnormalities, Multiple↗

PubMed2002

Secondary nonresponsiveness to new bulk botulinum toxin A (BCB2024).

We report on a patient with cranio-cervical dystonia injected with the new, lower protein formulation of botulinum toxin A who developed secondary resistance to this toxin. Subsequent injections with botulinum toxin B provided substantial reduction of blepharospasm. This is the first reported case of secondary resistance to the new preparation of botulinum toxin A.

Blepharospasm↗

PubMed2002

Clinical features and comorbidity of mood fluctuations in Parkinson's disease.

Parkinson's disease (PD) patients commonly develop fluctuations in their motor responses to levodopa within several years of initiation of treatment; some also develop nonmotor fluctuations. The authors performed a case-control study comparing the frequency of comorbid symptoms in 70 PD patients who experienced clinically apparent mood changes during their motor "on" or "off" states with two control groups with no mood fluctuations. Mood fluctuators had significantly younger age at onset and longer disease duration and were significantly more likely to have dementia, psychosis, clinical depression, and motor complications. This association remained after removing effects of age and disease duration.

Adult↗