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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
PubMed1994

X inactivation patterns in female monozygotic twins and their families.

X inactivation studies have been carried out on 22 pairs of female monozygotic twins, one set of female monozygotic triplets, and their mothers and singleton sisters, using the probe M27 beta. Forty-eight per cent of the twins, 55% of their mothers, and 42% of their singleton sisters showed skewed X inactivation. Two of the triplets and their mother had random X inactivation, while the third triplet showed skewed X inactivation. Their singleton sister was homozygous with M27 beta. Of the twins, six pairs showed skewed X inactivation in favour of the same X chromosome, one pair showed skewed X inactivation favouring opposite X chromosomes, in seven pairs one twin showed skewed X inactivation while her co-twin showed random X inactivation, and in eight pairs both twins were random. A higher frequency of skewed pattern of X inactivation was not observed in the monozygotic twins when compared to a series of non-twin females (mothers and singleton sisters) and, so, the results in this study do not lend support to the theory that skewed X inactivation predisposes to the twinning process.

Adult↗
PubMed1994

Family studies in Prader-Willi syndrome.

Clinical, cytogenetic and molecular studies have been undertaken in the families of 52 probands with Prader-Willi syndrome. The maternal age at the birth of a proband with a deletion in 15p11q13 was on average 8 years less than that of the mothers of probands with uniparental disomy (UPD), the paternal age was on average 7 years less. Seven probands with UPD were all female, as were 7 patients who had neither a detectable chromosomal abnormality nor UPD. Cytogenetic and molecular polymorphisms in proximal chromosome 15 indicated that for probands with a 15q11q13 deletion, inheritance of both the maternal and the intact paternal homologue is random in their unaffected sublings. Pigmentation studies suggest that probands who have a deletion in 15q11q13 have lighter colouring than other family members implying that D15S12 may not be imprinted.

Adult↗
PubMed1994

Environmental health. Nappies: the bottom line.

Increasing use of disposable nappies presents a major environmental hazard. Manufacturing processes consume vast amounts of resources; disposal is a significant pollution problem, although laundering nappies too generates pollution. Teresa Webb believes parents should be presented with the comparable facts about nappies, to enable them to make an informed choice.

Disposable Equipment↗
PubMed1993

Difference in methylation patterns within the D15S9 region of chromosome 15q11-13 in first cousins with Angelman syndrome and Prader-Willi syndrome.

Abnormalities of chromosome region 15q11-13 are associated with Angelman syndrome (AS) and Prader-Willi syndrome (PWS). Differences between the methylation patterns of the region of chromosome 15q11-13 which hybridizes to the highly conserved DNA, DN34, in normal individuals and in patients with AS and PWS have been described. We report on a family in which first cousins are affected by AS and PWS as a result of a familial paracentric inversion of 15q11-q13. The results of the studies on this family demonstrate the differences in the methylation patterns in the 2 conditions and the phenomenon of genomic imprinting, whereby genetic information is expressed differently dependent on the parent of origin.

Angelman Syndrome↗
PubMed1993

Neither uniparental disomy nor skewed X-inactivation explains Rett syndrome.

The locus DXS255 was studied using the probe M27 beta in ten probands with Rett syndrome and in eight of their families. No evidence of uniparental disomy of the X chromosome was detected, as all informative probands had inherited an allele from each of their parents. Differential methylation of a CCGG site within the DXS255 locus as shown by digestion with MspI/HpaII, revealed moderate skewing of X-inactivation favouring the maternal allele in two of the probands. Random X-inactivation was present in all mothers tested and in two unaffected sisters. Three of four unaffected siblings had inherited the same maternal allele at DXS255.

Alleles↗
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↗