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Biomedical subjects

T Webb

Publications and source records attributed to T Webb.

At least 73 records · Page 4Linked to original sources
PubMed1993

Prevalence of the fragile X anomaly amongst autistic twins and singletons.

Early screening studies of autistic individuals suggested that up to one-quarter of cases were associated with the Fragile X anomaly. Recent studies find that the usual behavioural phenotype of the Fragile X anomaly is distinct from autism as usually defined, and that a variety of methodological factors contribute to the variability of the prevalence estimates. We report the prevalence of the Fragile X anomaly, using strict cytogenetic criteria, in a large sample of autistic individuals whose diagnosis was confirmed using a standardised diagnostic instrument. The anomaly was detected in 1.6% of tested autistic individuals from a combined sample of: autistic twins; clinic attenders; and, individuals from families multiplex for autism or related cognitive phenotypes. The anomaly was not detected in greater than 2.5% of any of the constituent samples and accounted for only a small proportion of the genetic influences amongst concordant twins and multiplex families. The anomaly was detected in 5% of the 40 tested autistic females, confirming reports that the prevalence of the anomaly is similar amongst autistic individuals of both sexes.

Adult↗
PubMed1993

Molecular mechanisms in Angelman syndrome: a survey of 93 patients.

Angelman syndrome (AS) results from a lack of maternal contribution from chromosome 15q11-13, arising from de novo deletion in most cases or rarely from uniparental disomy. These families are associated with a low recurrence risk. However, in a minority of families, more than one child is affected. No deletion has been found in these families, except one. The mode of inheritance in these families is autosomal dominant modified by imprinting. Sporadic cases, with no observable deletion, therefore pose a counselling dilemma as there could be a recurrence risk as high as 50%. We present a series of 93 AS patients, showing the relative contribution of these different genetic mechanisms. Eighty-one AS patients were sporadic cases while 12 cases came from six families. Sixty cases had deletions in 15q11-13 detected by a set of highly polymorphic (CA)n repeats markers and conventional RFLPs. Ten sporadic cases plus all 12 familial cases had no detectable deletion. In addition, two cases of de novo deletions occurred in a chromosome 15 carrying a pericentric inversion. In one of these the AS child had a cousin with Prader-Willi syndrome (PWS) arising from a de novo deletion in an inv(15) inherited from his father. One case arose from a maternal balanced t(9;15)(p24;q15) translocation. There were three cases of uniparental disomy. Five patients were monoallelic for all loci across the minimal AS critical region, but the presence of a deletion cannot be confirmed. In familial cases, all affected sibs inherited the same maternal chromosome 15 markers for the region 15q11-13. Two cases were observed with a de novo deletion starting close to the locus D15S11 (IR4-2R), providing evidence for the development of classical AS with smaller deletions. Cytogenetic analysis proved limited in its ability to detect deletions, detecting only 42 out of 60 cases. However, cytogenetic analysis is still essential to detect chromosomal abnormalities other than deletions such as inversions and balanced translocations since both have an increased risk for deletions. A staged diagnostic strategy based on the use of highly informative (CA)n repeat markers is proposed.

Angelman Syndrome↗
PubMed1993

Duplication of chromosome 15 in the region 15q11-13 in a patient with developmental delay and ataxia with similarities to Angelman syndrome.

Duplications of the proximal long arm of chromosome 15 have been seen in the Prader-Willi syndrome (PWS), and in subjects without the Prader-Willi phenotype but with other clinical features including short stature, diabetes, anal and jejunal atresia, and acanthosis nigricans. The non-PWS subjects all had different phenotypes despite the identical findings on cytogenetic analysis. A normal phenotype has also been observed in patients with similar duplications. We report a further patient with a duplication of 15q11-13 which was detected cytogenetically and confirmed on molecular genetic analysis. She has developmental delay, particularly concerning the acquisition of speech, and an ataxic gait. These are interesting clinical features in view of the association of Angelman syndrome with abnormalities of 15q11-13.

Angelman Syndrome↗
PubMed1993

Information transmission in bilingual, bicultural contexts: a field study of community health nurses and interpreters.

The purpose of this article is to present the findings made in a field study of nurses and interpreters who were working in a county health department. Informed by the qualitative research method of grounded theory, analysis of 37 semistructured interviews revealed three types of interactions among nurses, interpreters, and clients. In these situations, the interpreter worked as a voice box, an excluder, or a collaborator. Collaborative interactions allowed both interpreters and community health nurses to establish the most effective rapport with clients. Rapport, in turn, facilitated client assessment and the planning and delivery of nursing services. Implications for community health nursing practice include providing opportunities for interpreters to establish a rapport with clients. Research implications include the development of strategies that promote collaboration between community health nurses and interpreters. Theoretically, such strategies would enhance client outcomes.

Communication↗
PubMed1993

Inheritance of parental chromosomes 15 in Angelman syndrome--implications for the family.

Molecular and cytogenetic studies in Angelman syndrome have demonstrated that the condition is genetically heterogeneous with a recurrence risk in certain families which may be as high as 50%. In an attempt to identify such families, cytogenetic polymorphisms of chromosome 15 have been studied in both affected and unaffected siblings of Angelman syndrome patients. The results suggest that in those cases with a cytogenetically visible 15q11q13 deletion where the recurrence risk is low, normal siblings inherit either maternal chromosome 15 homologue with impunity. By contrast, in cases where the proband does not demonstrate a cytogenetic 15q11q13 deletion, unaffected siblings tend to inherit the alternative homologue to that found in their affected siblings. These findings may have importance for genetic counseling.

Angelman Syndrome↗
PubMed1992

Further evidence for dominant inheritance at the chromosome 15q11-13 locus in familial Angelman syndrome.

Eleven patients with Angelman syndrome (AS) and their parents from 5 families have been studied with high resolution chromosome analysis and molecular probes from region 15q11-13 in an attempt to elucidate the mode of inheritance in familial AS. No deletions were detected. All families were informative with a combination of different short arm cytogenetic markers. All sets of sibs inherited the same maternal chromosome 15, but in 3 families sibs inherited different paternal 15s. Analysis of 6 polymorphic DNA markers supported the conclusion that AS sibs inherit the same maternal 15, but often different paternal 15s. These data make autosomal recessive inheritance at a 15q11-13 locus very unlikely and support the hypothesis that familial AS is due to maternal transmission of a mutation within 15q11-13.

Angelman Syndrome↗
PubMed1992

Delayed replication of Xq27 in individuals with the fragile X syndrome.

The timing of late replicating bands on the X chromosome has been studied in individuals with the fragile X [fra(X)] syndrome. Compared to controls both affected individuals and symptomless carriers of the syndrome show delayed replication of the Xq27 region as shown by 2 different methods. The implications of this finding are discussed in relation to the proposal [Laird et al., 1987] that the fraX syndrome is associated with a failure to reactivate the Xq27 band correctly after it has been inactivated in a female.

DNA↗
PubMed1992

A reinvestigation of thirty three fragile(X) families using probe StB12.3.

We have reinvestigated 33 fragile X families using probe StB12.3. In 31 families the affected individual showed an insert while in 2 families no insert was detected. The insert fell into two size categories: small (less than 0.5 kb); and large (greater than 0.6 kb) accompanied by methylation of an EagI site. All individuals of either sex having a small insert were fra(X) negative and intellectually normal, while all males having a large insert were fra(X) positive and intellectually impaired. Females having a large insert were either fra(X) positive or negative and either intellectually normal or impaired. No new mutation was found. All daughters of males with a small insert had a small insert; females with a large insert produced males and females who had a large insert, while females with a small insert had offspring with either a large or a small insert. However, females with a small insert tended to fall into one of two categories: either they had only children with a small insert or only children with a large insert, there being only one exception to this rule. We found four unexpected small inserts, two in unrelated spouses and two in female carriers who proved to be compound heterozygotes, indicating that they had inherited an insert from both their parents. These observations suggest that individuals with a small insert must be not uncommon in the general population.

DNA Probes↗
PubMed1992

Maternal origin of deletion 15q11-13 in 25/25 cases of Angelman syndrome.

About half of the cases of Angelman syndrome arise from deletions of chromosome band 15q12. In 25 cases we have been able to determine the parental origin of the deletion and, in line with other reported cases, we have found the deletion to be of maternal origin. There were no exceptions. The parental origin was determined using cytogenetic markers in 13 of the cases, in nine by using the pattern of inheritance of restriction fragment length polymorphisms, and in three using both techniques.

Abnormalities, Multiple↗
PubMed1992

X-inactivation in girls with Rett syndrome.

Cytogenetic studies have been carried out on a series of nine girls with Rett syndrome, six of their mothers and nine normal female controls. No abnormality of the X-chromosome has been observed in any subject. X-inactivation studies using various methods of detecting the timing of individual band replication were performed. The overall pattern seen was essentially the same in all subjects, but in the patients with Rett syndrome there may be an alteration in the timing of the X-inactivation process in the region Xp11.3 or 4-->Xp21.

Adolescent↗
PubMed1992

Angelman syndrome with a chromosomal inversion 15 inv(p11q13) accompanied by a deletion in 15q11q13.

A family is described in which an inversion of chromosome 15, 15 inv(p11q13), is segregating. All family members are healthy except the proband who is a 10 year old boy with Angelman syndrome. Although the chromosomal inversion has been passed from the grandfather to both his son and his daughter with no ill effect, passage from daughter to grandson has resulted in a deletion of chromosome 15 material which is presumed to be the cause of Angelman syndrome in this boy. The probabilities of an inversion of this type being instrumental in causing the syndrome are discussed.

Angelman Syndrome↗
PubMed1992

Expression of the fragile-X in the "premutated"/"non-imprinted" state.

Data about the expression of the fragile site at Xq27.3 from 74 daughters of normal transmitting males (NTMs) were collected from 7 different genetic centers. The majority (85.1%) of these obligate female carriers did not show any cytogenetic expression of fra-X. The remaining 14.9% of these females had frequencies below 3%. In cases with a frequency below 3% of fra-X, a "premutated"/"non imprinted" state of a female carrier should be considered. The results of this collaborative study are in accordance with data from DNA studies taking the premutation model into account.

Female↗
PubMed1992

Role of the independent duty corpsman on the USNS Comfort (T-AH 20): the Operation Desert Shield/Desert Storm experience.

Independent duty corpsmen (IDCs) have a significant role in providing health care on the USNS Comfort (T-AH 20). The IDCs are responsible for staffing sick call, emergency response teams, and resuscitation/stabilization teams. IDCs are trained in advanced patient care and in medical administrative and logistical duties. During peacetime, their function often focuses on primary care to the decrement of skills necessary to perform in medical emergencies. The Operation Desert Shield/Desert Storm mobilization has emphasized the need for Navy medicine to continue its support of IDC training so that they are kept in a state of preparedness to competently deliver the full spectrum of care that is expected of them.

Allied Health Personnel↗
PubMed1991

Uniparental paternal disomy in Angelman's syndrome.

Angelman's syndrome and Prader-Willi syndrome are both causes of mental retardation with recognisable, but quite different, clinical phenotypes. Both are associated with deletions of chromosome 15q11-13, of maternal origin in Angelman's and paternal in Prader-Willi. Prader-Willi can arise by inheritance of two chromosomes 15 from the mother and none from the father (uniparental maternal disomy). In 2 patients with Angelman's syndrome we found evidence of uniparental paternal disomy. The phenotypic effects of maternal and paternal disomy of chromosome 15 are very different and inheritance of two normal 15s from one parent does not lead to normal development--strong evidence in man for genomic imprinting, in which the same gene has different effects dependent upon its parental origin.

Alleles↗
PubMed1991

Expression of fragile-X in a female fetus diagnosed after chorionic villus sampling.

Study of different tissues of an aborted female fetus showed similar levels of fragile-X expression (6.3-9.2 per cent) and of early replication of the FRAXA-positive cells (50-66 per cent) in fetal tissues. Different culture media did not significantly affect either investigation. It is suggested that the distribution of X-inactivation in FRAXA-positive chorionic villus cells of a female fetus might indicate her future phenotype.

Cells, Cultured↗
PubMed1991

Moderate and mild mental retardation in the Martin-Bell syndrome.

A survey of children attending schools for the moderately or the mildly mentally handicapped has shown that two out of 25 boys and two out of 22 girls with idiopathic moderate mental retardation had the Martin-Bell syndrome, while none of 75 boys and one out of 51 girls with mild mental retardation were FRAXA positive. Consideration of these figures along with published studies suggests that 7% of moderate and 3.8% of mild idiopathic mental retardation in boys, and 2.5% of moderate and 3.3% of mild idiopathic mental retardation in girls may be due to the Martin-Bell syndrome.

Child↗