PubMed Health⌕ Search

Biomedical subjects

Michael Fitzgerald

Publications and source records attributed to Michael Fitzgerald.

At least 19 recordsLinked to original sources
PubMed2005

Association analysis of the monoamine oxidase A and B genes with attention deficit hyperactivity disorder (ADHD) in an Irish sample: preferential transmission of the MAO-A 941G allele to affected children.

Pharmacological and genetic studies suggest the importance of the dopaminergic, serotonergic, and noradrenergic systems in the pathogenesis of attention deficit hyperactivity disorder (ADHD). Monoamine oxidases A and B (MAO-A and MAO-B) degrade biogenic amines such as dopamine and serotonin and thereby control the levels of these neurotransmitters in the central nervous system. We examined four polymorphisms in the MAO-A gene (30 bp promoter VNTR, CA microsatellite in intron 2, 941G/T SNP in exon 8, and A/G SNP in intron 12) as well as two markers in the MAO-B gene (CA microsatellite in intron 2 and T/C SNP in intron 13) for association with ADHD in an Irish sample of 179 nuclear families. TDT analysis of the examined MAO-A markers revealed a significant association of the more active MAO-A 941G allele with the disorder (chi2 = 5.1, P = 0.03, OR = 1.7). In addition, haplotype analysis revealed a significantly increased transmission of a haplotype consisting of the shorter allele of the promoter VNTR (allele 1), the 6-repeat allele of the CA microsatellite and the G-allele of the 941G/T SNP (famhap global statistic 34.54, P = 0.01) to ADHD cases. No significant distortion in the number of transmitted alleles was observed between the two examined MAO-B polymorphisms and ADHD. These findings suggest the importance of the 941G/T MAO-A polymorphism in the development of ADHD at least in the Irish population.

Adult↗
PubMed2004

Multiple marker analysis at the promoter region of the DRD4 gene and ADHD: evidence of linkage and association with the SNP -616.

Abnormalities of dopamine neurotransmission have been hypothesized to play an important role in the pathophysiology of attention deficit hyperactivity disorder (ADHD). Support for this has come from numerous association studies on candidate genes including the dopamine D4 receptor gene (DRD4). One of the most replicated associations between ADHD and the dopaminergic system is the 7-repeat allele of the VNTR polymorphism of this gene. A lack of association between this marker and ADHD has also been reported in several investigations. In the absence of a firm link between the number of the VNTR repeats and the function of the gene, we sought to investigate several additional markers at the 5'-end of the gene with potential influence on the expression of the DRD4. We observed a significant over transmission of single nucleotide polymorphism (SNP) (chi(2) = 7.45, P = 0.008, OR = 1.63). In addition, an excess transmission of the A allele of the -521 SNP was observed, although it did not attain statistical significance (chi(2) = 2.14, P = 0.17, OR = 1.25). Linkage disequilibrium (LD) analysis demonstrated a weak level of D' between any of the tested markers implying that this may be a region of high recombination. It also raises the possibility that the new association with ADHD may be independent of the 7-repeat allele. Further analyses, preferably in samples demonstrating association with the VNTR, or in other ethnic groups, are required to confirm these observations.

Adult↗
PubMed2004

Phenotype studies of the DRD4 gene polymorphisms in ADHD: association with oppositional defiant disorder and positive family history.

The objective of this study was to investigate association of DRD4 polymorphisms with ADHD subtypes for which there is evidence for increased heritability. The genetic variants tested were the 120 bp insertion/deletion, the -616, -521, -376, and the 48 bp DRD4 VNTR. The primary analyses were of association with oppositional defiant disorder (ODD), conduct disorder (CD), and diagnostic subtypes. Secondary analyses of clinical subtype were exploratory in nature and included analysis of association of DRD4 polymorphisms with family history of ADHD. We observed significant association between DRD4 7-repeat allele transmission and ADHD children with comorbid ODD (chi(2) = 6.74, df = 1, P = 0.01, OR = 2.45) The DRD4 7-repeat allele was also significantly associated with family history positive ADHD (chi(2) = 10.12, df = 1, P = 0.0021, OR = 3.57). We observed no significant distortion in the transmission of any of the tested DRD4 variants with inattentive or hyperactive-impulsive subtypes or symptom dimensions. In conclusion, our findings of increased DRD4 7-repeat allele transmission in ODD extend those reported by Holmes et al. To our knowledge, this is the first study to report association of the DRD4 7-repeat allele with ADHD children who have a positive family history of ADHD. Overall, the results from this study support the investigation of clinical subtypes in molecular genetic studies of ADHD.

Adult↗
PubMed2004

Synthesis and structure-activity relationships of a novel series of 2,3,5,6,7,9-hexahydrothieno[3,2-b]quinolin-8(4H)-one 1,1-dioxide K(ATP) channel openers: discovery of (-)-(9S)-9-(3-bromo-4-fluorophenyl)-2,3,5,6,7,9- hexahydrothieno[3,2-b]quinolin-8(4H)-one 1,1-dioxide (A-278637), a potent K(ATP) opener that selectively inhibits spontaneous bladder contractions.

Structure-activity relationships were investigated on a novel series of sulfonyldihydropyridine-containing K(ATP) openers. Ring sizes, absolute stereochemistry, and aromatic substitution were evaluated for K(ATP) activity in guinea pig bladder cells using a fluorescence-based membrane potential assay and in a pig bladder strip assay. The inhibition of spontaneous bladder contractions in vitro was also examined for a select group of compounds. All compounds studied showed greater potency to inhibit spontaneous bladder contractions relative to their potencies to inhibit contractions elicited by electrical stimulation. In an anesthetized pig model of myogenic bladder overactivity, compound 14 and (-)-cromakalim 1 were found to inhibit spontaneous bladder contractions in vivo at plasma concentrations lower than those that affected hemodynamic parameters. Compound 14 showed approximately 5-fold greater selectivity than 1 in vivo and supports the concept that bladder-selective K(ATP) channel openers may have utility in the treatment of overactive bladder.

Adenosine Triphosphate↗
PubMed2004

An efficient multigram synthesis of the potent histamine H3 antagonist GT-2331 and the reassessment of the absolute configuration.

GT-2331 is a potent histamine H(3) antagonist which has entered clinical trials. Efficient multigram syntheses of this compound and its enantiomer are described. The literature reports that GT-2331 is the dextrorotatory (+), more potent, enantiomer of 4-[2-(5,5-dimethylhex-1-ynyl)cyclopropyl]-1H-imidazole with the absolute configuration of (1R,2R)-1. However, we found that the dextrorotatory, more potent, enantiomer of 4-[2-(5,5-dimethylhex-1-ynyl)cyclopropyl]-1H-imidazole has the (1S,2S) absolute configuration. We suggest a reconsideration of the absolute configuration of GT-2331.

Crystallography, X-Ray↗
PubMed2004

No association between allelic variants of HOXA1/HOXB1 and autism.

Two recent studies have reported conflicting findings of association of a variant in the HOXA1 gene and autism. To try to resolve the conflict in findings, we conducted an association study in 78 Irish families of the reported DNA variants. We did not find statistically significant association between the variants and autism. Similarly there was no evidence of preferential transmission of variants from parent of either sex to affected offspring. We also report negative findings for HOXB1 variants. We conclude that the HOXA1/B1 are unlikely to be the susceptibility genes for autism in our sample.

Alleles↗
PubMed2004

Humor in autism and Asperger syndrome.

Research has shown that individuals with autism and Asperger syndrome are impaired in humor appreciation, although anecdotal and parental reports provide some evidence to the contrary. This paper reviews the cognitive and affective processes involved in humor and recent neurological findings. It examines humor expression and understanding in autism and Asperger syndrome in the context of the main psychological theories (Theory of Mind, Executive Functions, Weak Central Coherence and Laterization models) and associated neural substrates. In the concluding sections, examples of humor displayed by individuals with autism/Asperger syndrome which appear to challenge the above theories are analyzed and areas for further research are suggested.

Affect↗
PubMed2004

Did Michelangelo (1475-1564) have high-functioning autism?

In this paper evidence is presented that Michelangelo met the criteria for Asperger's disorder, or high-functioning autism. The evidence relates to his single-minded work routine, unusual lifestyle, limited interests, poor social and communication skills, and issues of life control. Depression and various medical conditions, including gout, renal colic and renal stones, did not stop his obsessive working habits.

Art↗
PubMed2003

Association of the 480 bp DAT1 allele with methylphenidate response in a sample of Irish children with ADHD.

Several studies have implicated the dopamine transporter gene (DAT1) as conferring susceptibility to attention deficit hyperactivity disorder (ADHD), in particular, a VNTR situated at the 3' end of the gene. In addition, the 10-repeat VNTR allele associated with ADHD has been reported to be associated with an over-active transporter protein (DAT). Thus children possessing this variant might be particularly responsive to methylphenidate, a drug known to act by blocking DAT. We have examined this hypothesis and now report an association between the 10-repeat VNTR DAT1 polymorphism and retrospectively rated methylphenidate response in a sample of 119 Irish children with ADHD (chi(2) = 7.918, df = 1, P = 0.005). Our findings suggest a role for the 10-repeat DAT1 risk allele in medication response and may help to predict positive clinical outcome in ADHD.

Attention Deficit Disorder with Hyperactivity↗
PubMed2003

Plasma amino acid levels in children with autism and their families.

Plasma amino acid levels were measured in autistic and Asperger syndrome patients, their siblings, and parents. The results were compared with values from age-matched controls. Patients with autism or Asperger syndrome and their siblings and parents all had raised glutamic acid, phenylalanine, asparagine, tyrosine, alanine, and lysine (p < .05) than controls, with reduced plasma glutamine. Other amino acids were at normal levels. These results show that children with autistic spectrum disorders come from a family background of dysregulated amino acid metabolism and provide further evidence for an underlying biochemical basis for the condition.

Adolescent↗
PubMed2003

Brief report: A case of autism associated with del(2)(q32.1q32.2) or (q32.2q32.3).

Autism is a neurodevelopmental disorder presenting in the first 3 years of life. Deficits occur in the three core areas of communication, social interaction, and behavior. The causes of autism are unknown, but clinical genetic studies show strong evidence in favor of a genetic etiology. Molecular genetic studies report some association with candidate genes, and candidate regions have emerged from several genome-wide linkage studies. Here we report a clinical case of autism with a deletion on chromosome 2 in a young male with high-functioning autism. The deletion seems to correspond with regions emerging from linkage studies. We propose this as a possible candidate region in the search for autism genes.

Adolescent↗
PubMed2002

Association of DRD4 in children with ADHD and comorbid conduct problems.

Recent family and twin study findings suggest that ADHD when comorbid with conduct problems may represent a particularly familial and heritable form of ADHD. Although several independent groups have shown association between the DRD4 7 repeat allele and ADHD, others have failed to replicate this finding. Previous TDT analyses of UK and Eire samples had also been negative. We set out to further examine the role of DRD4 but selecting a subgroup of children with ADHD and comorbid conduct problems. Families were recruited from Manchester, Ireland, Birmingham and London clinics. From these, 67 children who fulfilled diagnostic criteria for ADHD and who displayed conduct disorder symptoms were selected. TDT analysis, which had previously yielded negative results for the total sample, showed evidence of association between DRD4 and "ADHD with conduct problems" (7 repeat allele-24 transmissions, 13 non-transmissions; one-tailed P=0.05). These results provide further support for the role of DRD4 in ADHD. Furthermore, these results when considered together with family and twin study findings, suggest that those children with ADHD and comorbid conduct problems may be particularly informative for molecular genetic studies of ADHD. Further work is needed to examine these phenotype issues.

Adolescent↗