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Biomedical subjects

N Ellis

Publications and source records attributed to N Ellis.

At least 19 recordsLinked to original sources

Evolution of the pseudoautosomal boundary in Old World monkeys and great apes.

Mammalian sex chromosomes are divided into sex-specific and pseudoautosomal regions. Sequences in the pseudoautosomal region recombine between the sex chromosomes; the sex-specific sequences normally do not. The interface between sex-specific and pseudoautosomal sequences is the pseudoautosomal boundary. The boundary is the centromeric limit to recombination in the pseudoautosomal region. In man, an Alu repeat element is found inserted at the boundary on the Y chromosome. In the evolutionary comparison conducted here, the Alu repeat element is found at the Y boundary in great apes, but it is not found there in two Old World monkeys. During the evolution of the Old World monkey and great ape lineages, homology between the sex chromosomes was maintained by recombination in the sequences telomeric to the Alu insertion site. The Alu repeat element did not create the present-day boundary; instead, it inserted at the preexisting boundary after the Old World monkey and great ape lineages diverged.

Animals

Population structure of the human pseudoautosomal boundary.

The mammalian sex chromosomes are composed of two genetically distinct segments: the pseudoautosomal region, where recombination occurs between the X and Y chromosomes, and the sex chromosome-specific parts. Between these two segments the human sex chromosomes differ by the insertion of an Alu element on the Y chromosome. We have surveyed the sequence variation in the boundary region using the polymerase chain reaction. Fifty seven Y and sixty X chromosomes from ten different human populations were analysed. The X chromosomes were found to be polymorphic at five positions in a 300-base-pair region. By contrast, all Y chromosomes were identical except for one distal polymorphism shared with the X chromosome.

Base Sequence

A reappraisal of the Malaise Inventory.

In recent years Rutter's Malaise Inventory has been used increasingly to measure levels of stress among those who care for people with dependency needs. Although there has been an element of dispute in the literature about the unidimensional nature of the scale, later work (Bebbington and Quine 1987) tends to suggest that Malaise Inventory scores can be used as a single internally consistent measure of stress. In this study consideration is given to the results of a national sample survey of 527 members of the Association of Carers (now Carers: National Association) which suggests the existence of two valid dimensions to the Malaise Inventory across a wider range of carer groups. Implications for future development and administration of the scale as a measure of stress are discussed.

Chronic Disease

The design of a stress-management programme for nursing personnel.

This study identifies the stressors and coping strategies of nursing staff (students, trained staff and those who had left the profession before qualification) in a variety of ward specialisms. The research instruments included an open-ended interview concerning pre-nursing experience, perceived stressors and satisfactions, and ways of coping, and psychometric tests of self-esteem, assertion, ways of coping and personality. The five most frequently cited stressors were understaffing, conflict with nurses, dealing with death and dying, overwork and conflict with doctors. Experience of stressors was related to role and seniority of respondents, with different aspects of the same stressor differentially affecting nurses at different levels of experience. Coping strategies also depended on experience. Trained staff showed more use of problem-focused ways of coping, whilst students and leavers relied more on emotion-focused strategies to deal with stressful situations. These differences were related to personality characteristics of respondents and to self-esteem as well as to situational characteristics of the stressful episode. Social support was important in times of work-related stress, with students in particular making good use of peer group support. Respondents were generally lacking in assertiveness and high in anxiety. Although self-esteem was generally high, leavers scored markedly less than other subject groups in the areas of personal and social self-esteem. Leavers had little prior knowledge or experience of nursing before entering training and knew few nurses or doctors: consequently, nursing failed to meet their expectations. Stress was identified as the major cause of attrition and the sources of stress are identified. This study informed a major programme of stress-management training for student nurses which began in 1988 at the North Wales School of Nursing and which is currently under evaluation. It includes relaxation therapy, assertiveness training, and on-going group discussions which foster peer-group support and which explore the stressors and coping strategies relevant to different stages of training and ward specialisms.

Adaptation, Psychological

Charity advertising: for or against people with a mental handicap?

This research investigated whether it is possible for charity advertising campaigns to stimulate donations successfully as well as to represent people with disabilities as valued human beings. Thirty-eight subjects were required to rank 10 MENCAP posters along 15 bipolar constructs using a variation of the Q sort procedure. Constructs included feelings such as pity, guilt and sympathy, constructive helping behaviours such as giving money and time, and perceptions such as having rights, value and capabilities. Correlational, cluster and factor analyses suggest that images which elicit the greatest commitment to give money are those most closely associated with feelings of guilt, sympathy and pity and are negatively associated with posters which illustrate people with a mental handicap as having the same rights, value and capability as non-handicapped persons. The implications of these findings with regard to advertising and the principle of normalization (social role valorization) are discussed.

Adolescent

Community health staff's prejudice and knowledge about AIDS.

Health service workers' attitudes to their patients carry significant health care consequences. In order to investigate the relationships between health workers' attitudes to groups at high risk of AIDS and their knowledge of the disease and views on procedures for care, community health care workers and students completed a social distance questionnaire concerning groups defined by ethnicity, sexual proclivity, or illness. There was strong negativity towards individuals of minority sexual proclivity and AIDS high risk groups. Fear of the disease and ignorance of its transmission and effective care procedures increase with prejudice towards these groups. Analysis of their relevant prior learning experiences demonstrates the need for an educational programme which addresses the identified sources of ignorance and which also necessarily concentrates on the prejudices which serve as a barrier to effective patient care.

Acquired Immunodeficiency Syndrome

Strong linkage disequilibrium between the XY274 polymorphism and the pseudoautosomal boundary.

The pseudoautosomal boundary is defined by an Alu repeat element on the Y chromosome. The Alu element is found on all Y chromosomes and on no X chromosomes, establishing it as part of Y-specific sequences. Distal to the Alu element, sequences from the X and Y are strictly homologous, suggesting that the boundary is formed by an abrupt break in sequence homology. Further investigation of the function of the boundary has been undertaken by examining the population structure of an MspI restriction-site polymorphism (XY274), which is located 274 bp distal to the Alu insertion site. Southern blot and polymerase chain reaction analysis demonstrate fixation of the high allele (noncutting or AT base pair) of XY274 on the Y chromosome in most populations, while a full range of high allele frequencies is found on the X chromosomes of different populations. Two exceptions to fixation on the Y chromosome were found in African populations. The level of linkage disequilibrium suggests that the first few hundred base pairs of the pseudoautosomal region on the Y chromosome share a single common origin more recent than the origin of the species.

Base Sequence

The mammalian pseudoautosomal region.

Despite being morphologically dissimilar, mammalian sex chromosomes pair in male meiosis. Molecular studies of the X and Y chromosomes in humans and mice have identified the pseudoautosomal region, a genetically unique region of shared, recombining sequences that fall within the meiotic pairing region. Complete meiotic and physical maps of the human pseudoautosomal region have been produced and the pseudoautosomal boundary has been cloned and sequenced. These studies have provided clues to mammalian sex chromosome function and evolution.

Animals

Isolation of a complementary DNA clone encoding a precursor to human eosinophil major basic protein.

A 14-kD protein was purified from human PMNs and its NH2-terminal sequence was determined. Comparison of a portion of the NH2-terminal sequence of this protein to the recently reported NH2-terminal sequence of eosinophil major basic protein (MBP) showed them to be identical. To aid further characterization of the structural and functional properties of this molecule, we isolated from an HL-60 cDNA library a single class of cDNA clones whose sequence matched exactly the NH2-terminal amino acid sequence of the 14-kD polypeptide. Northern analysis of HL-60 cells suggests that MBP is constitutively expressed in HL-60 cells and is highly transcribed from a single copy gene. The sequence of the full-length cDNA clones predicts that MBP is synthesized as a 23-kD precursor form (pro-MBP) which is subsequently cleaved to release the mature 14-kD MBP. The putative pro-MBP has a predicted pI of 6.0, but both the charged and the hydrophobic residues are asymmetrically distributed, creating a bipolar molecule. The NH2-terminal half has a predicted pI of 3.7 and is hydrophilic, while the COOH-terminal half (corresponding to mature MBP) has a predicted pI of 11.1 and is hydrophobic.

Base Sequence

MIC2: a human pseudoautosomal gene.

MIC2 and XGR are the only known pseudoautosomal genes in man. MIC2 encodes the 12E7 antigen, a human cell-surface molecule of unknown function. XGR regulates, in cis, the expression of the XG and MIC2 genes. DNA probes derived from the MIC2 locus have been used in the construction of a meiotic map of the pseudoautosomal region and a long range restriction map into the X- and Y-specific chromosome domains. MIC2 is the most proximal marker in the pseudoautosomal region and recombination between the sex chromsomes only rarely includes the MIC2 locus. Our long-range restriction maps and chromosome walking experiments have localized the pseudoautosomal boundary within 40 kilobases adjacent to the 3' end of the MIC2 gene. The same maps have been used to predict the chromosomal location of TDF.

Amino Acid Sequence

High-frequency reactivation of X-linked genes in Chinese hamster X human hybrid cells.

Three genes on the human inactive X chromosome retained in the Chinese hamster X human hybrid cell line X8/6T2 have been reactivated using the demethylating agent, 5-azacytidine (5-aza-CR). Pulse-labeling and histochemical methods permitted detection and measurement of reactivation rates of the hypoxanthine phosphoribosyltransferase (Hpt) and glucose-6-phosphate dehydrogenase (G6pd) genes within 48 h of treatment. About 50% of the cells became active for these genes, which represents a reactivation rate some 30-fold greater than previously reported in similar systems. The phosphoglycerate kinase (Pgk) gene was not reactivated as frequently as the Hpt or G6pd genes. Segregation analysis of progeny of treated cells showed that enzyme-positive and enzyme-negative cells were produced in proportions supporting the notion that 5-aza-CR causes demethylation by replicative loss and that demethylation leads to reactivation.

Animals

The development of reading: as you seek so shall you find.

In this paper we critically examine different methods of investigation of reading development and reading disability. We argue that there is need for longitudinal studies of reading where a differential design allows assessment of the relative degree of involvement of associated skills. We then describe one study of this type. The results chart the development of children who become skilled readers and of those with generalized or specific reading disability. They also demonstrate the crucial effects of decisions regarding subject matching, test design, and measurement of differential abilities on the outcomes of such investigations. A cohort of 40 children was assessed for their abilities on 44 variables which involved reading, spelling, vocabulary, short-term memory (STM), visual skills, auditory-visual integration, language knowledge, rote knowledge and ordering ability as they developed from five to eight years old. Three groups were extracted at age eight on the basis of reading and IQ scores. Group A showed a relatively specific reading disability (high IQ, low reading), Group B were good readers of similarly high IQ, Group C showed a more generalized reading deficit whereby they were at the same level as Group A in reading but their IQ scores were low. The data were then searched retrospectively to describe the development of these patterns of ability from the very beginnings of reading acquisition. The children with specific reading retardation differed from their better-reading peers in terms of relatively few variables which concerned phonological segmentation, STM and naming. The children with generalized reading disability differed from their better-reading peers in almost every respect, but the strong discriminators concerned phonological processing. The children with specific reading disability differed from those with generalized reading disability in terms of abilities which involve visual processing. These patterns of ability were replicated at each age from five to seven years old.

Achievement

High rate of somatic point mutation in vitro in and near the variable-region segment of an immunoglobulin heavy chain gene.

The "silent" allele at the immunoglobulin heavy-chain locus in the pre-B-lymphocyte line 18-81 contains a correctly assembled gene. However, an amber termination codon within the variable-region gene segment prematurely terminates translation into complete heavy chain. Revertants that do produce heavy chain are generated at a high rate, which is termed hypermutation. By DNA sequencing of subclones, we have confirmed that whenever mu chain is produced by the usually silent allele, a true reversion is found in the DNA. Mutations are not confined to the position of the amber termination codon but are also found at other sites in and near the variable-region gene segment.

Base Composition

Blowgun dart aspiration.

We report on two young patients with unusual airway foreign bodies: blowgun darts. These homemade darts are constructed with yarn, thread, and a common pin. Because only the pin is radiopaque, and because the child may be reluctant to disclose the nature of the foreign body, the bronchoscopist may encounter unexpected difficulty in extracting the dart. A radiograph showing a pin head down in the trachea or bronchus, coughing (especially with hemoptysis) in excess of that expected from just an aspirated pin, and a child hesitant to divulge the full history suggest blowgun dart aspiration.

Bronchi