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Biomedical subjects

A J Dawson

Publications and source records attributed to A J Dawson.

At least 19 recordsLinked to original sources
PubMed2005

Seeing, thinking and acting against Malaria: a new approach to health worker training for community empowerment in rural Gambia.

CONTEXT: In the Gambia, West Africa, Malaria is a major cause of death among children in rural areas. It has been estimated that in one division in the country malaria accounts for 40% of all deaths in children aged between one and 4 years. Most malaria cases are managed at home assisted by primary healthcare workers. The strategic plan of Gambia's National Malaria Control Programme includes improved training and supervision of all health care providers, at all levels, and increased community awareness in order to reduce the malaria burden by 50% before 2007. ISSUE: A malaria in-service training program for Community Health Nurses (CHNs) working at village level was piloted in 2004. The program includes a computer-based training (CBT) package, the first of its kind for health professionals in Gambia. The education program is part of a larger initiative funded by the Gates Malaria Partnership, that aims to increase community involvement in malaria control. The objective of the course is to enable CHNs to facilitate the change process. The curriculum was informed by a reference group and stakeholder input. Interviews and evaluation forms were used to gather information about learner experience and learning preferences. ANALYSIS: The CBT package was well received. Learners reported wanting more computer instruction, but felt they had gained confidence. There was resistance from other health professionals regarding the development of information technology skills in CHNs. This related to the perceived role and status of CHNs, as well as confidence in their ability. Some modifications of the CBT package were necessary, including the reworking of some activities and language. LESSONS LEARNED: There are issues related to sustainability and resource implications that need to be addressed. Opportunities exist to expand e-learning in the Gambia for pre-service CHNs and other professionals. An investigation into the viability of reproducing this module as a generic planning tool for allied health workers and other extension workers at community level will be undertaken.

Adult↗
PubMed2005

Fibreoptic intubation skills among anaesthetists in New Zealand.

The aim of this study was to investigate methods of practice, assess skill level, and evaluate attitudes towards fibreoptic intubation in the anaesthetic community of New Zealand. A postal survey questionnaire was sent to all vocationally registered anaesthetists in New Zealand and to all New Zealand anaesthetic trainees registered with the Australian and New Zealand College of Anaesthetists. There were 611 survey questionnaires posted and 386 (63%) respondents. Almost all respondents (98% of specialists, 100% of trainees) had access to fibreoptic equipment in public and 92% of respondents performed fibreoptic intubation. The median number of fibreoptic intubations performed per year was 3 for consultants and 4 for trainees. Respondents were either self taught or colleague taught (82%). Most learnt the technique on patients (92%). There were 14% who considered themselves experienced, 30% competent, 34% adequate and 20% novice. Skills were maintained by clinical patient mix in 73%. Fibreoptic intubation was considered a skill required by all anaesthetists in 87%, and 66% considered it the gold standard for expected difficult airways. Lack of clinical cases requiring the skill and lack of practice were identified as the primary barriers to skill development. Consultants had greater opportunity to learn fibreoptic intubation skills during daily practice than trainees. Only 18% of trainees had a formal airway management program available to them at their place of work. There appears to be a need to increase available opportunities to perform fibreoptic intubation to enable maintenance and improvement of fibreoptic skills in our community. A formalized program of teaching fibreoptic intubation may offer greater opportunity for learning and skill development.

Adult↗
PubMed2004

A unique patient with an Ullrich-Turner syndrome variant and mosaicism for a tiny r(X) and a partial proximal duplication 1q.

A 7-year old female with global cognitive impairment, short attention span, hyperactivity, impulsivity, and many compulsive behaviors was referred to the Genetics Clinic. Height was below the 5th centile and weight was at the 5th centile while head circumference was at the 50th centile. Minor anomalies included bluish sclera, low set and slightly posteriorly rotated auricles and a narrow palate with marked overbite. There was no significant family history. Chromosome analysis showed an unbalanced, mosaic female karyotype consisting of three cell lines: 46,X,+r[46]/45,X[37]/45,X,dup(1)(q11q21.3) [17] de novo.ish r(X)(DXZ1+,XIST+). Expression of XIST was observed in cDNA from the patient, suggesting the presence of an inactive X chromosome. Inactivation was confirmed by detection of a methylated allele of androgen receptor. This methylated allele was under-represented in undigested DNA, consistent with it arising from the r(X) which was present in only a minority of the patient's cells. The clinical phenotype of the tiny r(X) syndrome in our patient is obviously further influenced by mosaicism for the dup(1). Few cases of duplication of the proximal portion of chromosome 1 have been reported. Of these, the duplication either was present in all cells or involved different band regions so that a direct comparison would be difficult. However, the lower percentage of mosaicism for the dup(1) in our patient would suggest a milder influence on the clinical phenotype.

Child↗
PubMed2003

Interstitial deletion of chromosome 2p16.2p21.

We report on a female who presents with an atrial septal defect (ASD), mild hypotelorism, a prominent nasal bridge, a long smooth philtrum, mild developmental delay and a de novo interstitial deletion of the short arm of chromosome 2p, del (2)(p16.2p21). This is the first report of a deletion in chromosome 2 involving those particular breakpoints. We propose that this may represent a new recognizable chromosomal phenotype.

Chromosome Aberrations↗
PubMed2002

Identification of a dup(5)(p15.3) by multicolor banding.

A 7-year-old female was referred to the Genetics Clinic because of developmental delay and attentional difficulty. The patient was adopted and there was a nonspecific prenatal history of drug and alcohol abuse. The patient had clinical signs that were not compatible with typical fetal alcohol syndrome (FAS), although there was a history of alcohol exposure in utero, neurodevelopmental difficulties with learning and behavioral problems, and mild dysmorphisms. Cytogenetic analysis revealed an unbalanced female karyotype with a dup(5) containing additional chromosome 5 material at band 5p15.3. The dup(5) showed normal copy number of the cri-du-chat region on 5p15.2 using locus-specific probes D5S721 and D5S23. Multicolor banding of chromosome 5 (MetaSystems) using partial chromosome paint (pcp) probes showed a duplication of band 5p15.3. The karyotype of the patient was therefore interpreted as follows: 46,XX,add(5)mat.ish dup(5)(p15.3)(wcp5 +, D5S271 +, D5S23 +, C84C11/T3 + +, pcp5p15.3 + +). The patient's biological mother and maternal half-brother were found to carry the identical chromosome duplication. The clinical phenotype of the biological mother is complicated by a difficult lifestyle but there were apparent learning and behavioral difficulties at school. The half-brother is nondysmorphic and presents with learning problems and attention deficit disorder (ADD). His physical examination was normal. To the best of our knowledge, this is the first report of a limited duplication of 5p15.3. The clinical significance of the dup(5)(p15.3) is still uncertain but may be the basis for learning and attention difficulties.

Abnormalities, Multiple↗
PubMed2002

Cryptic chromosome rearrangements detected by subtelomere assay in patients with mental retardation and dysmorphic features.

The regions near telomeres of human chromosomes are gene rich. Chromosome subtelomere rearrangements occur with a frequency of 7-10% in children with mild-to-moderate mental retardation (MR) and approximately 50% of cases are familial. Clinical investigation of subtelomere rearrangements is now prompted by fluorescence in situ hybridization (FISH) analysis using specific DNA probes from all relevant chromosome ends. In our study, 40 children were selected for subtelomere assay using either the Chromophore Multiprobe-T Cytocell device or the VYSIS TelVision probes. Inclusion criteria were: developmental delay or MR; a normal 550 G-band karyotype; FRAXA negative; and at least one other clinical criterion. Exclusion criteria included an identified genetic or environmental diagnosis. Of the 40 patients analysed, four (10%) were found to have subtelomere rearrangements. Three of 40 (7.5%) were found to have an unbalanced subtelomere rearrangement and one of 40 (2.5%) was found to have an apparently normal variant subtelomere deletion. The first of the three with an unbalanced karyotype was the result of a familial translocation, the second was a de novo finding, and the origin of the third could not be determined. The subtelomere FISH assay detected almost twice the frequency of unbalanced karyotypes as those detected by 550 G-banding in our cytogenetics laboratory (4.7%). In addition, subtelomere screening was eight times more likely than fragile X screening in our DNA laboratory (1%) to detect genetic abnormalities in mentally handicapped individuals. Our findings support the view that screening for subtelomere rearrangements has a greater positive yield than other commonly used genetic investigations and, if cost and resources permit, should be the next diagnostic test of choice in a child with unexplained MR/dysmorphisms and a normal 550 G-band karyotype.

Abnormalities, Multiple↗
PubMed2001

Mosaic trisomy of a small r(1) with an abnormal phenotype.

Cytogenetic studies of a mildly dysmorphic 10-year-old male with mild developmental delay and learning difficulties revealed mosaicism for a supernumerary ring chromosome in approximately half of the cells. The karyotype of this patient was established as 47,XY,+r[15]/46,XY[15].ish r(1)(D1Z7+,wcp1-). Although the presence of euchromatic material was shown by C banding, the lack of hybridization with the whole chromosome paint 1 (wcp1) probe suggests that few unique sequences are contained in the ring and that these sequences likely explain the child's dysmorphic features and developmental delay. A review of the literature, including the present case, suggests that the significance of euchromatin in supernumerary r(1) as determined by both C banding and fluorescence in situ hybridization (FISH) with chromosome 1 painting probes can be used as a prognostic indicator for potential severity of the clinical phenotype.

Child↗
PubMed2001

Regenerating optic fibers correct large-scale errors by random growth: evidence from in vivo imaging.

Regenerating optic fibers in goldfish make large-scale errors when they invade tectum and subsequently correct these to generate a projection with moderate retinotopic order by 1 month. The behavior of fibers underlying these extensive rearrangements is not well understood. To clarify this, we have imaged optic fibers in living adult goldfish at 2-4 weeks of regeneration. A small number of neighboring retinal ganglion cells were labeled with microinjections of DiI and imaged in the dorsal tectum with a cooled CCD camera on a fluorescence microscope for 5 to 8 hours. Nearly all fibers were simple unbranched processes and had endings that were highly dynamic showing both growth and retraction. Fibers from dorsal retina that normally innervate ventral tectum were frequently observed in dorsal tectum. These ectopic fibers oscillated more frequently between growth and retraction and retracted more often than ventral optic fibers. Like retinotopic fibers, ectopic fibers exhibited net growth but they showed no apparent directional preference toward their retinotopic position. In contrast, large errors along the anterior-posterior axis corresponding to nasal-temporal retina were rare and there was no differential behavior that distinguished these fibers.

Animals↗
PubMed2001

De novo interstitial long arm deletion of chromosome 3 with facial dysmorphism, Dandy-Walker variant malformation and hydrocephalus.

We report an 8-year-old girl with coarse facial features, macrocrania and developmental delay. Cranial anomalies in the form of hydrocephalus and Dandy-Walker (DW) variant malformation were detected on neuro-imaging. Karyotyping revealed a de novo interstitial deletion of bands 3q25.1 to 3q25.33. Deletion of the 3q24-q26 region appears to be associated with a somewhat similar constellation of findings of craniofacial dysmorphism (broad and depressed nasal bridge and low set posteriorly rotated ears), mental retardation, congenital heart defects, and central nervous system malformations.

Child↗
PubMed1999

Activity-dependent refinement in the goldfish retinotectal system is mediated by the dynamic regulation of processes withdrawal: an in vivo imaging study.

Imaging of regenerating optic fibers in living adult goldfish was used to visualize arbor restructuring during activity-dependent refinement. A small number of neighboring retinal ganglion cells were labeled with DiI and observed in the tectum of the living animal for 5-7 hours during the period of activity-dependent refinement. In contrast to earlier stages of regeneration, many optic arbors were surprisingly stable, showing little or no change. The observed changes were mainly retractions, and these were affected by retinotopic position and activity. Axon branches in retinotopic positions changed by much smaller amounts than ectopic axons, but in fish with retinal tetrodotoxin impulse blockade, no systematic difference was observed as a function of tectal position. Otherwise, impulse blockade had no notable effects.

Animals↗
PubMed1998

Vertical transmission of the Ohdo blepharophimosis syndrome.

Ohdo blepharophimosis syndrome (OBS) is a multiple congenital anomalies-mental retardation syndrome composed of blepharophimosis, ptosis, dental hypoplasia, partial deafness, and mental retardation. Previously reported cases of OBS have been sporadic except for the report by Ohdo et al. [1986, J Med Genet 23:242-244] that described two affected sisters and a first cousin favoring autosomal recessive inheritance. The original report by Ohdo et al. [1986] may reflect nonpenetrance of an autosomal dominantly inherited disorder or genetic heterogeneity of OBS. We report on a child and the mother who have blepharophimosis, ptosis, dental anomalies, mild hearing loss, and mental retardation. Chromosome analysis in both showed a balanced paracentric inversion of the long arm of chromosome 9, which was also present in two phenotypically normal sibs of the mother. This is the first report of vertical transmission of OBS suggestive of autosomal dominant inheritance. X-linked dominant and mitochondrial inheritance are other possible modes of inheritance.

Abnormalities, Multiple↗
PubMed1998

Transmission of the FRAXA haplotype from three nonpenetrant brothers to their affected grandsons: an update with AGG interspersion analysis.

Recently, we reported on a family showing transmission of the FRAXA gene by three nonpenetrant, normally intelligent, full and half brothers to their affected grandsons [Kirkilionis et al., 1992]. We have reanalyzed this family for CGG repeat size by polymerase chain reaction (PCR) amplification/Southern blot and FMR1 methylation status using EcoRI/BssHII double digests with pE5-1 as the hybridization probe. The half brother was found to have a premutation allele size of 59 CGG repeats. MnlI digestion of PCR products showed the absence of intervening AGG sequences. All of his obligate carrier daughters had CGG alleles ranging from 65 to 90 repeats, with a final expansion of more than 200 repeats in his FRAXA-affected grandson and 131 repeats in his carrier granddaughter. Two full brothers were shown to have inherited a 47-CGG repeat premutation allele. Analysis of one brother showed that he stably transmitted the 47-repeat allele to his daughter. Analysis of the second brother, his daughter, and his granddaughter showed that this allele was meiotically unstable, with the allele size increasing from 47, to 48, to 49 from the father, to the daughter to the granddaughter, respectively. MnlI digestion and DNA sequencing of PCR products showed the absence of intervening AGG sequences. This is the first case in which the lack of AGG interspersions has been associated with instability of a gray zone allele resulting in a one-repeat increase in two successive generations.

Adenosine↗