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Biomedical subjects

S Keeney

Publications and source records attributed to S Keeney.

At least 19 recordsLinked to original sources
PubMed2006

Mutations that affect meiosis in male mice influence the dynamics of the mid-preleptotene and bouquet stages.

Meiosis pairs and segregates homologous chromosomes and thereby forms haploid germ cells to compensate the genome doubling at fertilization. Homologue pairing in many eukaryotic species depends on formation of DNA double strand breaks (DSBs) during early prophase I when telomeres begin to cluster at the nuclear periphery (bouquet stage). By fluorescence in situ hybridization criteria, we observe that mid-preleptotene and bouquet stage frequencies are altered in male mice deficient for proteins required for recombination, ubiquitin conjugation and telomere length control. The generally low frequencies of mid-preleptotene spermatocytes were significantly increased in male mice lacking recombination proteins SPO11, MEI1, MLH1, KU80, ubiquitin conjugating enzyme HR6B, and in mice with only one copy of the telomere length regulator Terf1. The bouquet stage was significantly enriched in Atm(-/-), Spo11(-/-), Mei1(m1Jcs/m1Jcs), Mlh1(-/-), Terf1(+/-) and Hr6b(-/-) spermatogenesis, but not in mice lacking recombination proteins DMC1 and HOP2, the non-homologous end-joining DNA repair factor KU80 and the ATM downstream effector GADD45a. Mice defective in spermiogenesis (Tnp1(-/-), Gmcl1(-/-), Asm(-/-)) showed wild-type mid-preleptotene and bouquet frequencies. A low frequency of bouquet spermatocytes in Spo11(-/-)Atm(-/-) spermatogenesis suggests that DSBs contribute to the Atm(-/-)-correlated bouquet stage exit defect. Insignificant changes of bouquet frequencies in mice with defects in early stages of DSB repair (Dmc1(-/-), Hop2(-/-)) suggest that there is an ATM-specific influence on bouquet stage duration. Altogether, it appears that several pathways influence telomere dynamics in mammalian meiosis.

Animals↗
PubMed2006

Initiation of meiotic recombination by formation of DNA double-strand breaks: mechanism and regulation.

Homologous recombination is essential for accurate chromosome segregation during meiosis in most sexual organisms. Meiotic recombination is initiated by the formation of DSBs (DNA double-strand breaks) made by the Spo11 protein. We review here recent findings pertaining to protein-protein interactions important for DSB formation, the mechanism of an early step in the processing of Spo11-generated DSBs, and regulation of DSB formation by protein kinases.

Animals↗
PubMed2005

The molecular analysis of haemophilia A: a guideline from the UK haemophilia centre doctors' organization haemophilia genetics laboratory network.

Haemophilia A is a common inherited bleeding disorder that has a well-understood pathophysiology. Our understanding of the molecular genetics of the disease has allowed the development of comprehensive carrier and prenatal diagnosis for this single gene defect. Continuing technological developments improve our ability to provide genetic analysis in a rapid and cost effective manner. This guideline aims to provide advice on current best laboratory practice when approaching genetic diagnosis of haemophilia A.

Base Sequence↗
PubMed2005

The molecular analysis of haemophilia B: a guideline from the UK haemophilia centre doctors' organization haemophilia genetics laboratory network.

Haemophilia B is one of the most common inherited bleeding disorders and has a well understood pathophysiology. Our understanding of the molecular genetics of the disease has allowed the development of comprehensive carrier and prenatal diagnosis for this single gene disorder. Continuing technological developments improve our ability to provide genetic analysis in a rapid and cost-effective manner. This guideline aims to provide advice on current best laboratory practice when approaching genetic diagnosis of haemophilia B.

Base Sequence↗
PubMed2004

A common ancestral mutation (C128X) occurring in 11 non-Jewish families from the UK with factor XI deficiency.

Factor XI (FXI) deficiency is a mild bleeding disorder that is particularly common in Ashkenazi Jews, but has been reported in all populations. In Jews, two FXI gene (F11) mutations (a stop codon in exon 5, E117X, type II, and a point mutation in exon 9, F283L, type III) are particularly common, but in other populations a variety of different mutations have been described. In the Basque region of France one mutation, C38R in exon 3, was found in eight of 12 families studied, haplotype analysis suggesting a founder effect. In the course of screening 78 unrelated individuals (including 15 Jewish and 12 Asian) we have found 10 Caucasian non-Jewish patients with the mutation C128X in exon 5. Individuals were investigated because of a personal or family history of bleeding, or finding a prolonged activated partial thromboplastin time. Individuals negative for the type II and type III mutations were screened by a combination of SSCP and heteroduplex analysis. The C128X mutation was found in 10 families (one previously described). Among three individuals with severe FXI deficiency, one was homozygous for the C128X mutation, and two were compound heterozygotes for the C128X and another mutation; other individuals were carriers of the C128X mutation. This is a nonsense mutation producing a truncated protein; individuals have FXI antigen levels concordant with FXI coagulant activity. Haplotype analysis of 11 families, including a further kindred previously reported from the USA, but which originally came from the UK (in which the index patient was homozygous for C128X), suggests a founder effect.

Adolescent↗
PubMed2001

Meiotic recombination: Making and breaking go hand in hand.

Accurate segregation of homologous chromosomes at the first meiotic division requires the tight coordination of DNA replication, homologous recombination and chromosome organization. Recent studies suggest that the initiation of meiotic recombination is mechanistically coupled to premeiotic DNA replication.

DNA Replication↗
PubMed2001

A critical review of the Delphi technique as a research methodology for nursing.

The Delphi technique is an approach used to gain consensus among a panel of experts. This is normally achieved through a series of rounds where information is fed back to panel members using questionnaires. It has been used extensively within social science research and is being increasingly employed by nurse researchers. This popularity has meant that the technique has been adapted in various ways and there is the possibility that the rigour associated with the original format has been threatened. This signals the need for a critical review of the Delphi as a robust and systematic approach to data collection. While there is a great volume of literature surrounding the "Delphi", there is a dearth of papers critically analysing the technique. This paper aims to examine critically the Delphi technique from a range of perspectives. Discussion will focus on problems of definition and the advantages and disadvantages and the techniques' application in nursing. The critique will be structured through an analysis of the key aspects of the Delphi process. These key aspects include analysis of sampling, anonymity, use of experts, rounds and application. The critical analysis highlights the increasing popularity of the Delphi and the modifications to the process which may cause methodological problems. Ultimately, the Delphi has much to offer in terms of gaining consensus from a wide range of individuals on specific topics.

Communication↗
PubMed2001

Mechanism and control of meiotic recombination initiation.

Homologous recombination is essential during meiosis in most sexually reproducing organisms. In budding yeast, and most likely in other organisms as well, meiotic recombination proceeds via the formation and repair of DNA double-strand breaks (DSBs). These breaks appear to be formed by the Spo11 protein, with assistance from a large number of other gene products, by a topoisomerase-like transesterase mechanism. Recent studies in fission yeast, multicellular fungi, flies, worms, plants, and mammals indicate that the role of Spo11 in meiotic recombination initiation is highly conserved. This chapter reviews the properties of Spo11 and the other gene products required for meiotic DSB formation in a number of organisms and discusses ways in which recombination initiation is coordinated with other events occurring in the meiotic cell.

Amino Acid Sequence↗
PubMed2001

Recombinational DNA double-strand breaks in mice precede synapsis.

In Saccharomyces cerevisiae, meiotic recombination is initiated by Spo11-dependent double-strand breaks (DSBs), a process that precedes homologous synapsis. Here we use an antibody specific for a phosphorylated histone (gamma-H2AX, which marks the sites of DSBs) to investigate the timing, distribution and Spo11-dependence of meiotic DSBs in the mouse. We show that, as in yeast, recombination in the mouse is initiated by Spo11-dependent DSBs that form during leptotene. Loss of gamma-H2AX staining (which in irradiated somatic cells is temporally linked with DSB repair) is temporally and spatially correlated with synapsis, even when this synapsis is 'non-homologous'.

Animals↗
PubMed2001

The molecular biology of von Willebrand disease.

von Willebrand disease (VWD) is a common autosomally inherited bleeding disorder associated with mucosal or trauma-related bleeding in affected individuals. VWD results from either a quantitative or qualitative deficiency of von Willebrand factor (VWF)--a glycoprotein with essential roles in primary haemostasis and as a carrier of coagulation factor VIII (FVIII) in the circulation. In recent years the identification of mutations in the VWF gene in patients with VWD has improved our understanding of the structure and function of the VWF protein, and has illustrated the importance of specific regions of VWF for its interaction with other components of the vasculature. The underlying genetic lesions and associated molecular pathology have been identified in many cases of type 2A, type 2B, type 2M, type 2N and type 3 VWD. However in the most common variant, type 1 VWD, the causative molecular defect is unknown in the large majority of cases. In the absence of an understanding of the molecular pathology underlying type 1 VWD, precise diagnosis and classification of this common disorder remains problematic.

Family Health↗
PubMed2000

Progression of meiotic DNA replication is modulated by interchromosomal interaction proteins, negatively by Spo11p and positively by Rec8p.

Spo11p is a key mediator of interhomolog interactions during meiosis. Deletion of the SPO11 gene decreases the length of S phase by approximately 25%. Rec8p is a key coordinator of meiotic interhomolog and intersister interactions. Deletion of the REC8 gene increases S-phase length, by approximately 10% in wild-type and approximately 30% in a spo11Delta background. Thus, the progression of DNA replication is modulated by interchromosomal interaction proteins. The spo11-Y135F DSB (double strand break) catalysis-defective mutant is normal for S-phase modulation and DSB-independent homolog pairing but is defective for later events, formation of DSBs, and synaptonemal complexes. Thus, earlier and later functions of Spo11 are defined. We propose that meiotic S-phase progression is linked directly to development of specific chromosomal features required for meiotic interhomolog interactions and that this feedback process is built upon a more fundamental mechanism, common to all cell types, by which S-phase progression is coupled to development of nascent intersister connections and/or related aspects of chromosome morphogenesis. Roles for Rec8 and/or Spo11 in progression through other stages of meiosis are also revealed.

Chromosomes, Fungal↗
PubMed2000

Chromosome synapsis defects and sexually dimorphic meiotic progression in mice lacking Spo11.

Spo11, a protein first identified in yeast, is thought to generate the chromosome breaks that initiate meiotic recombination. We now report that disruption of mouse Spo11 leads to severe gonadal abnormalities from defective meiosis. Spermatocytes suffer apoptotic death during early prophase; oocytes reach the diplotene/dictyate stage in nearly normal numbers, but most die soon after birth. Consistent with a conserved function in initiating meiotic recombination, Dmc1/Rad51 focus formation is abolished. Spo11(-/-) meiocytes also display homologous chromosome synapsis defects, similar to fungi but distinct from flies and nematodes. We propose that recombination initiation precedes and is required for normal synapsis in mammals. Our results also support the view that mammalian checkpoint responses to meiotic recombination and/or synapsis defects are sexually dimorphic.

Adenosine Triphosphatases↗
PubMed2000

Discharge planning: an exploratory study.

The desire to reduce the length of waiting lists in the modern health service means that strategies for decreasing the length of hospital stay are exercising the minds of service planners. This has led to renewed emphasis on well planned discharge policies and procedures. The aim of this study was to analyse all discharge policies and procedures currently in use in one large integrated NHS trust in Northern Ireland and formulate a Corporate Discharge Policy for general use in NHS trusts. Objectives of the study included examining the current process of discharge, reviewing the interface between ward staff and district nursing services and examining the quality and standard of documentation in use. Findings indicate the need for standardization of the discharge planning process and sufficient notice of discharge, and for clarification and education regarding staff roles, the importance of multidisciplinary working, and the lack of quality communication between acute and community services.

Hospitals, Public↗
PubMed2000

An exploration of community psychiatric nursing: a Northern Ireland perspective.

The Audit Commission's (1994) report Finding a Place states that mental health problems are a major cause of disruption and difficulty in people's lives and that in any one year more than a quarter of all people suffer to some degree. The report asserts that the majority visit their general practitioner (GP) and less than half of the people concerned are recognized as having a mental health problem. Many recover over a period of weeks or months and are best served by community services. Only those with the most serious conditions need specialized care or admission to hospital. On a local level in Northern Ireland, the policy of reducing the number of long-stay patients began in the 1960s with a call for people with mental illness to be integrated into the community. This has had major implications for community mental health services and for community psychiatric nursing. The aim of this study into one community psychiatric nursing service (CPNS) in Northern Ireland is to inform managers and professionals about the nature and shape of this service and to facilitate wider discussion on how to plan and deliver it in the future.

Community Mental Health Services↗
PubMed2000

Research guidelines for the Delphi survey technique.

Consensus methods such as the Delphi survey technique are being employed to help enhance effective decision-making in health and social care. The Delphi survey is a group facilitation technique, which is an iterative multistage process, designed to transform opinion into group consensus. It is a flexible approach, that is used commonly within the health and social sciences, yet little guidance exists to help researchers undertake this method of data collection. This paper aims to provide an understanding of the preparation, action steps and difficulties that are inherent within the Delphi. Used systematically and rigorously, the Delphi can contribute significantly to broadening knowledge within the nursing profession. However, careful thought must be given before using the method; there are key issues surrounding problem identification, researcher skills and data presentation that must be addressed. The paper does not claim to be definitive; it purports to act as a guide for those researchers who wish to exploit the Delphi methodology.

Attitude of Health Personnel↗
PubMed1999

A mouse homolog of the Saccharomyces cerevisiae meiotic recombination DNA transesterase Spo11p.

The Saccharomyces cerevisiae Spo11 protein is thought to catalyze formation of the DNA double-strand breaks that initiate meiotic recombination. We have cloned cDNA and genomic DNA for a mouse gene encoding a protein with significant sequence similarity to conserved domains found in proteins of the Spo11p family. This putative mouse Spo11 gene maps to the distal region of chromosome 2 (homologous to human chromosome 20q13.2-q13.3) and comprises at least 12 exons, spanning approximately 15-18 kb. Strong expression of the Spo11 message is seen in juvenile and adult testis by RNA in situ hybridization, RT-PCR, and Northern blot, with much weaker expression in thymus and brain. In situ hybridization detects expression in oocytes of embryonic ovary, but not of adult ovary. RT-PCR and in situ hybridization analyses of a time course of juvenile testis development indicate that Spo11 expression begins in early meiotic Prophase I, prior to the pachytene stage, with increasing accumulation of mRNA through the pachytene stage. Taken together, these results strongly suggest that this gene encodes the functional homolog of yeast Spo11p, which in turn suggests that the mechanism of meiotic recombination initiation is conserved between yeast and mammals.

Amino Acid Sequence↗