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W Roberts

Publications and source records attributed to W Roberts.

At least 37 records · Page 2Linked to original sources
PubMed2000

Evidence for the serotonin HTR2A receptor gene as a susceptibility factor in attention deficit hyperactivity disorder (ADHD).

A recent study demonstrated that treatment of hyperactive mice with psychostimulants and serotonergic agents produced a calming effect that was dependent on serotonergic neurotransmission and was not associated with any changes in extracellular dopamine levels. The complex interaction between the serotonergic and dopaminergic neurotransmitter systems suggests that a balance between the two systems may be necessary for mediating hyperactive behaviour. Defects in serotonin system genes, therefore, may disrupt normal brain serotonin function causing an imbalance between these neurotransmitter systems leading to the development of attention deficit hyperactivity disorder (ADHD). Using the transmission disequilibrium test (TDT), the current study assesses for linkage disequilibrium between polymorphisms in the serotonin HTR2A receptor gene and ADHD. One hundred and fifteen families with a total of 143 children diagnosed with ADHD (DSM-IV) were genotyped for the His452 Tyr and the T102C polymorphisms in the serotonin HTR2A receptor gene. TDT analysis revealed a preferential transmission of the 452Tyr allele to the affected offspring (P = 0.03), suggesting linkage disequilibrium of this polymorphism with ADHD. This may open a new door in ADHD molecular genetics research, expanding the existing view of a catecholaminergic hypothesis to include a serotonergic hypothesis and should help elucidate the complex interplay among the neurotransmitter systems in the etiology of ADHD.

Adolescent↗
PubMed2000

Adverse response to methylphenidate in combination with valproic acid.

The use of methylphenidate (MPH) in combination with antiepileptic drugs is gaining acceptance for children with epilepsy who have the symptoms of attention-deficit hyperactivity disorder (ADHD). We report two cases of an adverse effect of dyskinesia and bruxism when MPH was given to children maintained on valproic acid. These adverse effects were rapid and severe. Because of the potential for serious and persistent side effects from this combination of medications, caution is warranted in the treatment of ADHD with MPH for children taking valproic acid. Further prospective studies of the use of valproic acid and MPH in combination are required.

Anticonvulsants↗
PubMed2000

Linkage of the dopamine D4 receptor gene and attention-deficit/hyperactivity disorder.

OBJECTIVE: There is considerable evidence supporting a genetic component in the etiology of attention-deficit/hyperactivity disorder (ADHD). Because stimulant medications act primarily on the dopaminergic system, dopamine system genes are prime candidates for genetic susceptibility factors for ADHD. Previous studies by several groups have observed a significant association of ADHD and an allele with 7 copies of the 48 base pair repeat in the third exon of the dopamine D4 receptor. METHOD: The authors sought to replicate these previous findings by collecting an independent sample of families from Toronto, Ontario, Canada, and confirming this finding in an expanded sample of ADHD families collected from Irvine, California. Using the transmission disequilibrium test (TDT), the authors tested for biased transmission of the 7-repeat allele at the exon III polymorphism of the dopamine D4 receptor locus in these samples of ADHD subjects. RESULTS: Biased transmission of the 7-repeat allele from parents to ADHD probands and their affected siblings was observed in the 2 new samples of families collected in Toronto and Irvine (TDT chi2 = 2.711, 1 df, one-sided p value = .050) and for these samples combined with the 52 families previously reported from Irvine (TDT chi2 = 6.426, 1 df, one-sided p value = .006). CONCLUSIONS: The results of this study further support the possibility of a role of the dopamine D4 receptor locus in ADHD.

Adolescent↗
PubMed1999

Linkage study of catechol-O-methyltransferase and attention-deficit hyperactivity disorder.

Attention-deficit hyperactivity disorder is the most common child psychiatric disorder with a prevalence rate in an Ontario study of 9% in boys and 3% in girls [Szatmari et al., 1989]. This disorder is characterized by problems in the areas of attention, overactivity, impulse control, and distractibility. Strong evidence for a genetic component has been provided from twin, family, and adoption studies [for review see Levy et al., 1998] and molecular genetic studies are in progress by several groups worldwide. The Catechol-O-Methyltransferase (COMT) gene is an interesting candidate for ADHD as it is involved in the breakdown of dopamine and norepinephrine, neurotransmitters strongly implicated in the etiology of ADHD. In addition, children with velo-cardio-facial syndrome, a deletion syndrome of the chromosomal region 22q11 where the COMT gene has been localized, often have symptoms of ADHD suggesting this gene may have an etiological role in ADHD. In this study, we have tested for linkage in ADHD families using the functional polymorphism at codon 158 that determines COMT activity [Lachman et al., 1996] and analyzed the data with the transmission disequilibrium test (TDT). A total of 77 nuclear families collected from Toronto were genotyped. We find no evidence for linkage of this polymorphism and ADHD in our sample. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 88:710-713, 1999.

Adolescent↗
PubMed1999

Effect of methylphenidate on attention in children with attention deficit hyperactivity disorder (ADHD): ERP evidence.

Methylphenidate is the most common treatment for attention deficit hyperactivity disorder (ADHD) and has been shown to improve attention and behaviour. However, the precise nature of methylphenidate on specific aspects of attention at different dose levels remains unclear. We studied methylphenidate effects in ADHD from a neurophysiological perspective, recording event-related potentials (ERPs) during attention task performance in normal controls and children with ADHD under different dose conditions. Twenty children with ADHD and 20 age matched controls were assessed with a continuous performance task requiring subjects to identify repeating alphabetic characters. ERPs and behavioural measures were recorded and analyzed for trials where a correct response was made. The ADHD group was assessed off drug (baseline) and on placebo, low (0.28 mg/kg) and high (0.56 mg/kg) dose levels of methylphenidate. The results showed that the ADHD group at baseline was more impulsive and inattentive than controls and had shorter P2 and N2 latencies and longer P3 latencies. Low dose methylphenidate was associated with reduced impulsivity (fewer false alarms) and decreased P3 latencies, whereas the higher dose level was associated with reduced impulsivity and less inattention (more hits), as well as increased P2 and N2 latencies and decreased P3 latencies. Amplitudes were unaffected and there were no adverse effects of the higher dose for any of the children. These results suggest differential dosage effects and a dissociation between dose levels and aspects of processing.

Attention↗
PubMed1999

Hematopoietic stem cell transplantation for childhood myeloid malignancies after high-dose thiotepa, busulfan and cyclophosphamide.

Seventeen children with advanced myeloid malignancies (induction failure, relapse, myelodysplasia, secondary AML, or CR >1) received thiotepa 750 mg/m2 i.v., busulfan 12 mg/kg or 640 mg/m2 p.o., and cyclophosphamide 120 mg/kg i.v. as a preparative regimen for allogeneic or autologous hematopoietic stem cell (HSC) transplantation. Of the 15 allogeneic transplants, eight were from matched siblings, one was from a mismatched sibling, and six were from unrelated donors. Graft-versus-host disease (GVHD) prophylaxis consisted of cyclosporine or tacrolimus and methotrexate. Regimen-related toxicity was common but tolerable, affecting mainly the skin and gastrointestinal tract. Three patients died early and were not evaluable for engraftment; engraftment occurred in the remaining patients. Nine patients with active disease at the time of transplant were evaluable for response; all achieved remission. With a median follow-up of 40 months (range, 10-71 months), nine patients are alive and disease-free. The 3-year actuarial event-free survival was 51% (95% confidence interval (CI) 27-76%). Seven patients died of transplant-related complications: infection (n = 4), chronic GVHD (n = 1), veno-occlusive disease, VOD, (n= 1) and pulmonary alveolar hemorrhage (n = 1). Only one patient had leukemia relapse and died. We conclude that the use of high-dose thiotepa, busulfan and cyclophosphamide is an effective conditioning regimen for childhood myeloid malignancies and may be tested in patients with less advanced disease (eg CR1).

Adolescent↗
PubMed1997

Personal references.

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Computer Communication Networks↗
PubMed1997

Expression of the human milk protein beta-casein in transgenic potato plants.

A 1177 bp cDNA fragment encoding the human milk protein beta-casein was introduced into Solanum tuberosum cells under control of the auxin-inducible, bidirectional mannopine synthase (mas1',2') promoters using Agrobacterium tumefaciens-mediated leaf disc transformation methods. Antibiotic-resistant plants were regenerated and transformants selected based on luciferase activity carried by the expression vector containing the human beta-casein cDNA. The presence of human beta-casein cDNA in the plant genome was detected by PCR and DNA hybridization experiments. Human beta-casein mRNA was identified in leaf tissues of transgenic plants by RT-PCR analysis. Human beta-casein was identified in auxin-induced leaf and tuber tissues of transformed potato plants by immunoprecipitation and immunoblot analysis. Human beta-casein produced in transgenic plants migrated in polyacrylamide gels as a single band with an approximate molecular mass of 30 kDa. Immunoblot experiments identified approximately 0.01% of the total soluble protein of transgenic potato leaf tissue as beta-casein. The above experiments demonstrate the expression of human milk beta-casein as part of an edible food plant. These findings open the way for reconstitution of human milk in edible plants for replacement of bovine milk in baby foods for general improvement of infant nutrition, and for prevention of gastric and intestinal diseases in children.

Caseins↗
PubMed1997

Use of nested polymerase chain reaction to identify feline herpesvirus in ocular tissue from clinically normal cats and cats with corneal sequestra or conjunctivitis.

OBJECTIVE: To use a nested polymerase chain reaction (PCR) to detect feline herpesvirus (FHV-1) DNA in conjunctiva or cornea from clinically normal cats and cats with conjunctivitis or corneal sequestra. SAMPLES: Conjunctival snip biopsy specimens from 50 cats with conjunctivitis and 50 clinically normal cats; 28 keratectomy specimens from 26 cats with sequestra, and 13 specimens from clinically normal cats. PROCEDURE: Tissue specimens were digested, and FHV-1 DNA was amplified, using a double round of PCR. Products were visualized by use of agarose gel electrophoresis. RESULTS: Polymerase chain reaction was positive in 27 of 50 (54%) conjunctival specimens from cats with conjunctivitis and 6 of 50 (12%) specimens from clinically normal cats. Difference in the results between cats with conjunctivitis and clinically normal cats was statistically significant. Polymerase chain reaction was positive in 5 of 28 (18%) corneal specimens from cats with sequestra and 6 of 13 (46%) clinically normal cats. Distribution of positive results between clinically normal cats and those with sequestra was not significant. CONCLUSION: Cats with conjunctivitis were more likely to have a positive PCR result than were clinically normal cats, making it likely that FHV-1 was associated with the disease state. Herpesvirus DNA could not be detected in most corneas from cats with sequestra. CLINICAL RELEVANCE: Polymerase chain reaction is a useful clinical test for identifying FHV-1 DNA in cats with conjunctivitis, yielding greater sensitivity over that of current available tests. Herpesvirus may be less of a cause of corneal sequestration in the commonly affected breeds, Himalayan and Persian, than other factors, such as lagophthalmos or corneal metabolic defects.

Acute Disease↗
PubMed1997

Comparison of nested polymerase chain reaction, virus isolation, and fluorescent antibody testing for identifying feline herpesvirus in cats with conjunctivitis.

OBJECTIVE: To compare nested polymerase chain reaction (PCR), virus isolation (VI), and fluorescent antibody (FA) testing to detect feline herpesvirus (FHV) in cats with naturally acquired conjunctivitis or respiratory tract disease, or both. SAMPLES: Swab and microbrush specimens from the conjunctiva and throat were taken from 46 cats, allotted to 3 groups (conjunctivitis only, respiratory tract disease and conjunctivitis, and clinically normal). PROCEDURE: Cells from microbrush specimens were digested and herpesvirus DNA was amplified, using a double round of PCR. Products were detected by use of agarose gel electrophoresis. The VI and FA tests were performed in routine manner. RESULTS: Of 16 cats with conjunctivitis only, conjunctival specimens from 8 and throat specimens from 8 were FHV positive by PCR. None had positive results of VI or FA testing. Of 15 cats with respiratory tract disease and conjunctivitis, conjunctival specimens from 13 and throat specimens from 12 were FHV positive by PCR. A conjunctival specimen from 1 cat and throat specimens from 3 cats were FHV positive by VI. A conjunctival specimen from 1 cat was FHV positive by FA testing. Of 15 clinically normal cats, conjunctival and throat specimens from 2 cats were FHV positive by PCR; neither conjunctival nor throat specimens from these cats were FHV positive by VI or FA testing. CONCLUSION: For cats with respiratory tract disease and conjunctivitis, or with conjunctivitis only, nested PCR was more sensitive at detecting FHV than was VI or FA testing. CLINICAL RELEVANCE: Nested PCR is a more sensitive test than the currently available VI and FA tests for identifying FHV in cats with conjunctivitis.

Animals↗
PubMed1996

Methylphenidate slows right hemisphere processing in children with attention-deficit/hyperactivity disorder.

To examine the effects and particularly, any potential detrimental effects of methylphenidate on right hemisphere processing in children with attention-deficit/hyperactivity disorder (ADHD), the performance of 26 children (aged 8-15 years) with ADHD was compared under methylphenidate and placebo on various cognitive tasks in a double-blind within-subjects design. Results indicated that reaction times on a tachistoscopic task were slower on methylphenidate for stimuli that produced a left visual field advantage (reflecting better right hemisphere functioning) but not for stimuli that produced a right visual field advantage (reflecting better left hemisphere functioning) or for bilateral stimuli. It is argued that methylphenidate induces a slower response on tasks involving right hemisphere processing, resulting in slower reaction times and unchanged accuracy rates. Findings on two tasks that more closely reflect classroom-type tasks revealed an improvement in performance on methylphenidate, suggesting that any stimulant-induced benefits on learning style may have overcome detrimental effects on unilateral processing. These findings may help understand the complex, diverse, and sometimes unpredictable effects of psychostimulants on cognitive functioning that are observed clinically in individuals treated for ADHD.

Adolescent↗
PubMed1996

One Touch II hospital system for neonates: correlation with serum glucose values.

A correlation study was conducted to examine the relationship between results from LifeScan's One Touch II blood glucose monitoring system and laboratory analysis of serum glucose values in neonates. A total of 327 blood samples was obtained from newborn infants in a Level III NICU. The comparison of the paired results showed that the r value was .902. The overall results suggest that the LifeScan One Touch II set in the neonatal mode gives results showing good agreement with standard serum glucose values in neonates with serum glucose values < 100 mg/dl (5.6 mmol/liter).

Blood Glucose↗
PubMed1996

Developmental monitoring in primary care.

Monitoring child development is an essential part of primary health care. Successful surveillance depends on physicians' thorough knowledge of normal progress along the four developmental streams: motor, language, cognitive, and social and emotional. Being alert to "red flags" that suggest problems is important. Effective interventions can minimize developmental problems.

Child↗