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Christine Murphy

Publications and source records attributed to Christine Murphy.

9 recordsLinked to original sources
PubMed2006

The Drosophila melanogaster Cajal body.

Cajal bodies (CBs) are nuclear organelles that are usually identified by the marker protein p80-coilin. Because no orthologue of coilin is known in Drosophila melanogaster, we identified D. melanogaster CBs using probes for other components that are relatively diagnostic for CBs in vertebrate cells. U85 small CB-specific RNA, U2 small nuclear RNA, the survival of motor neurons protein, and fibrillarin occur together in a nuclear body that is closely associated with the nucleolus. Based on its similarity to CBs in other organisms, we refer to this structure as the D. melanogaster CB. Surprisingly, the D. melanogaster U7 small nuclear RNP resides in a separate nuclear body, which we call the histone locus body (HLB). The HLB is invariably colocalized with the histone gene locus. Thus, canonical CB components are distributed into at least two nuclear bodies in D. melanogaster. The identification of these nuclear bodies now permits a broad range of questions to be asked about CB structure and function in a genetically tractable organism.

Animals↗
PubMed2004

Structure in the amphibian germinal vesicle.

The germinal vesicle (GV) of Xenopus laevis is an enormous nucleus that contains 18 giant lampbrush chromosomes and thousands of inclusions. The inclusions are primarily of three types: approximately 1500 extrachromosomal nucleoli, 50-100 Cajal bodies, and several thousand B-snurposomes, which correspond to speckles or interchromatin granule clusters in other nuclei. The large size and abundance of the GV organelles, as well as the ease with which they can be studied both in vivo and in vitro, make the GV an ideal object for analysis of nuclear structure and function.

Amphibians↗
PubMed2003

Steady-state dynamics of Cajal body components in the Xenopus germinal vesicle.

Cajal bodies (CBs) are evolutionarily conserved nuclear organelles that contain many factors involved in the transcription and processing of RNA. It has been suggested that macromolecular complexes preassemble or undergo maturation within CBs before they function elsewhere in the nucleus. Most such models of CB function predict a continuous flow of molecules between CBs and the nucleoplasm, but there are few data that directly support this view. We used fluorescence recovery after photobleaching (FRAP) on isolated Xenopus oocyte nuclei to measure the steady-state exchange rate between the nucleoplasm and CBs of three fluorescently tagged molecules: U7 small nuclear RNA, coilin, and TATA-binding protein (TBP). In the nucleoplasm, the apparent diffusion coefficients for the three molecules ranged from 0.26 to 0.40 microm2 s-1. However, in CBs, fluorescence recovery was markedly slower than in the nucleoplasm, and there were at least three kinetic components. The recovery rate within CBs was independent of bleach spot diameter and could not be attributed to high CB viscosity or density. We propose that binding to other molecules and possibly assembly into larger complexes are the rate-limiting steps for FRAP of U7, coilin, and TBP inside CBs.

Active Transport, Cell Nucleus↗
PubMed2002

Heat shock induces mini-Cajal bodies in the Xenopus germinal vesicle.

Cajal bodies are evolutionarily conserved nuclear organelles that are believed to play a central role in assembly of RNA transcription and processing complexes. Although knowledge of Cajal body composition and behavior has greatly expanded in recent years, little is known about the molecules and mechanisms that lead to the formation of these organelles in the nucleus. The Xenopus oocyte nucleus or germinal vesicle is an excellent model system for the study of Cajal bodies, because it is easy to manipulate and it contains 50-100 Cajal bodies with diameters up to 10 microm. In this study we show that numerous mini-Cajal bodies (less than 2 microm in diameter) form in the germinal vesicle after oocytes recover from heat shock. The mechanism for heat shock induction of mini-Cajal bodies is independent of U7 snRNA and does not require transcription or import of newly translated proteins from the cytoplasm. We suggest that Cajal bodies originate by self-organization of preformed components, preferentially on the surface of B-snurposomes.

Animals↗
PubMed2002

RNA polymerase III in Cajal bodies and lampbrush chromosomes of the Xenopus oocyte nucleus.

We used immunofluorescence to study the distribution and targeting of RNA polymerase (pol) III subunits and pol III transcription factors in the Xenopus laevis oocyte nucleus. Antibodies against several of these proteins stained Cajal bodies and approximately 90 specific sites on the lampbrush chromosomes. Some of the chromosomal sites had been identified previously by in situ hybridization as the genes for 5S rRNA. The remaining sites presumably encode tRNAs and other pol III transcripts. Pol III sites were often resolvable as loops similar to the much more abundant pol II loops, but without a matrix detectable by phase contrast or differential interference contrast. This morphology is consistent with the transcription of short repeated sequences. Hemagglutinin-tagged transcripts encoding core subunits and transcription factors were injected into the oocyte cytoplasm, and the distribution of newly translated proteins inside the nucleus was monitored by immunostaining. Cajal bodies were preferentially targeted by these proteins, and in some cases the chromosomal sites were also weakly stained. The existence of pol III subunits and pol III transcription factors in Cajal bodies and their targeting to these organelles are consistent with a model of Cajal bodies as sites for preassembly of the nuclear transcription machinery.

Amanitins↗
PubMed2002

Food and fluid intake and disturbances in gastrointestinal and mental function during an ultramarathon.

The purpose of this study was to document eating strategies employed by runners during a 160-km race, and to identify eating patterns that predispose the runner to disturbed mental or gastrointestinal functioning. We monitored intake in 19 volunteers during the 12 hours pre-race. Intake was determined by interview with runners approximately every 12 km throughout the race. The mean finish time was 24.3 hours, with 4 runners not completing the race. Body mass decreased during the race, 75.9 +/- 2.3 kg to 74.4 +/- 2.2 kg (p <.001). Runners ingested 2643 kcals during the 12 hours prerace (68% carbohydrate) and 3.8 L of fluid. During the race 6047 kcal, 18 L of fluid, and 12 g of sodium were consumed. Gastrointestinal distress (GI) was experienced by half of the participants, but was unrelated to food or fluid intake. Upper GI symptoms were more prevalent than lower and occurred mainly after 88 km. Runners with GI distress tended to complete fewer training miles (p =.10) and to do shorter training runs (p =.08). Half of the volunteers reported mental status changes (MSC), such as confusion or dizziness. Runners with MSC had greater intake of total calories, carbohydrate, and fluid (p <.05) than runners without MSC. They also completed shorter training runs (p =.03). Caloric and moisture intake for all runners far exceeded intakes described previously. Although intake did not match energy expenditure, it may represent the upper limit for absorption during exercise, and very high food and/or fluid intake appears to lead to perturbed mental status.

Adult↗
PubMed2002

Investors in people: progress in the PHLS.

In 1990 the government launched an initiative called Investors in People (IIP). The intention was clear: to improve operational performance in the workplace through effective business-focused training and development of employees. The market for the national standard that was created was also clear: every organisation throughout the UK, irrespective of size or sector. Implementation of IIP by the Public Health Laboratory Service (PHLS) is outlined, and four views of the process from across the Service are presented.

Humans↗
PubMedDate not supplied

The distribution of RNA polymerase II largest subunit (RPB1) in the Xenopus germinal vesicle.

We describe the localization of the largest subunit of RNA polymerase II (RPB1) in the oocyte nucleus of Xenopus laevis. A single oocyte nucleus contains 18 lampbrush chromosomes, approximately 1500 extrachromosomal nucleoli, 50-100 Cajal bodies (CBs) and hundreds to thousands of B-snurposomes. CBs contain many factors involved in RNA transcription and processing, whereas B-snurposomes contain a subset of these factors involved in mRNA processing. Immunofluorescent staining demonstrates that most RPB1 is in the nucleoplasm and that the heptapeptide repeat comprising its carboxy-terminal domain (CTD) is not phosphorylated. A minor fraction of RPB1 is associated with the transcription units of the lampbrush chromosomes and is phosphorylated on serines 2 and 5 of the CTD. Another minor fraction occurs in CBs, which react with antibodies against unphosphorylated CTD repeats and repeats phosphorylated on serine 5. Although B-snurposomes are stained by an antibody against phosphorylated RPB1 (mAb H5), we present evidence that this stain is due to cross-reaction with one or more SR proteins. We show that constructs consisting of 15-17 CTD heptapeptide repeats fused to glutathione-S-transferase are targeted rapidly and specifically to CBs but not to B-snurposomes after injection into the nucleus. The staining and targeting data define at least three distinct populations of RPB1 in the GV with different states of phosphorylation. We suggest that CBs play a unique role in RPB1 metabolism, possibly as sites for assembly or modification of transcription complexes.

Animals↗