Characterisation of the Schizosaccharomyces pombe rad4/cut5 mutant phenotypes: dissection of DNA replication and G2 checkpoint control function

Mutation of the essential Schizosaccharomyces pombe rad4/cut5 gene causes sensitivity to UV and ionising radiation at the permissive temperature whilst at the restrictive temperature cells fail to undergo DNA replication but still attempt mitosis owing to a defective S-phase checkpoint response. Many mutations in genes encoding DNA replication proteins also abolish checkpoint responses, possibly because the replication machinery is a pre-requisite for the generation of the signal. We demonstrate here that rad4/cut5 cells fail to arrest cell division when treated with the replication inhibitor hydroxyurea at the semi-permissive temperature 32 degrees C, but retain essentially normal replicative capacity. This demonstrates that the replication and checkpoint function of the rad4/cut5 gene product can be separated and that the Rad4 protein differs from other replication proteins in being directly involved in generating the S-phase checkpoint signal. Furthermore, we have investigated the checkpoint response or rad4/cut5-deficient cells to gamma-irradiation and UV-mimetic drugs. We find that, at the restrictive temperature, the rad4-/cut5- cells fail to delay mitosis in response to gamma-irradiation whilst retaining a normal checkpoint response to the UV-mimetic drug 4-nitroquinoline-1-oxide. The lack of the gamma-irradiation checkpoint is reminiscent of the deficiency associated with mutation of the human ATM locus, the causative deficiency of the heritable disorder ataxia telangiectasia. The implications of our results for the organisation of distinct checkpoint-response pathways in both fission yeast and mammalian cells are discussed. Moreover the data are consistent with a model in which the generation of the S-Phase checkpoint signal is DNA polymerase epsilon dependent.

Chromosomal localization of three human dual specificity phosphatase genes (DUSP4, DUSP6, and DUSP7)

Mitogen-activated protein (MAP) kinase phosphatases constitute a growing family of dual specificity phosphatases thought to play a role in the dephosphorylation and inactivation of MAP kinases and are therefore likely to be important in the regulation of diverse cellular processes such as proliferation, differentiation, and apoptosis. For this reason it has been suggested that MAP kinase phosphatases may be tumor suppressors. We have determined the chromosomal locations of three human dual specificity phosphatase genes by fluorescence in situ hybridization and radiation hybrid mapping. The genes were localized to three different chromosomes, MKP2 (DUSP4) to 8p11-p12, MKP3 (DUSP6) to 12q22-q23, and MKPX (DUSP7) to 3p21. This will allow the potential roles of these genes in disease processes to be evaluated.

Isolation of a Schizosaccharomyces pombe gene which in high copy confers resistance to the nucleoside analogue 5-azacytidine

Treatment of Schizosaccharomyces pombe with the C5 DNA methyltransferase (C5Mtase) inhibitor 5-azacytidine (5-azaC) has previously been shown to induce G2 checkpoint-dependent cell cycle arrest. S. pombe strains defective in both the checkpoint control pathways and in DNA repair processes are sensitive to 5-azaC. Here we describe the isolation of azr1+, as a multi-copy suppressor of the 5-azaC sensitivity of G2 checkpoint and DNA repair-deficient strains. azr1+ encodes a putative 25 kDa protein with limited homology to a Saccharomyces cerevisiae open reading frame of unknown function. The azr1+ gene is not essential and the null mutant shows no alteration in either DNA repair or checkpoint properties. We also report the sequence of the putative fission yeast cytidine deaminase gene, designated pcd1+, which lies immediately adjacent to azr1+ but which plays only a moderate role in suppression of 5-azaC sensitivity.

The structural components of music perception. A functional anatomical study

This work explores the cerebral structures involved in the appreciation of music. We studied six young healthy subjects (right handed, French, without musical talent), using a high resolution PET device (CTI 953B) and 15O-labelled water. In three tasks, we studied the effects of selective attention to pitch, timbre and rhythm; a final task studied semantic familiarity with tunes (considered as divided attention for pitch and rhythm). These four tasks were performed on the same material (a tape consisting of 30 randomly arranged sequences of notes). We selected a paradigm, without a reference task, to compare the activations produced by attention to different parameters of the same stimulus. We expected that the activations recorded during each task would differ according to the differences in cognitive operations. We found activations preferentially in the left hemisphere for familiarity, pitch tasks and rhythm, and in the right hemisphere for the timbre task. The familiarity task activated the left inferior frontal gyrus, Brodmann area (BA) 47, and superior temporal gyrus (in its anterior part, BA 22). These activations presumably represent lexico-semantic access to melodic representations. In the pitch task, activations were observed in the left cuneus/precuneus (BA 18/19). These results were unexpected and we interpret them as reflecting a visual mental imagery strategy employed to carry out this task. The rhythm task activated left inferior Broca's area (BA 44/6), with extention into the neighbouring insula, suggesting a role for this cerebral region in the processing of sequential sounds.

Symbolic anatomic knowledge representation in the Read Codes version 3: structure and application

The Read Thesaurus (Version 3 of the Read Codes) is a controlled medical vocabulary produced during the Clinical Terms Projects with the involvement of over 2,000 health care professionals from all United Kingdom specialties. In addition to allowing the transfer of clinical information in a meaningful way, it supports analysis of this information and provides a basis for the development of shareable medical knowledge bases. The thesaurus includes a comprehensive, dynamic set of over 7,000 gross anatomic concepts richly linked in a network with over 16,000 operative procedures and 40,000 disorders. The representation of anatomic concepts aims to balance the requirements for expressivity, clearness, and simplicity. The underlying directed acyclic graph hierarchy is independent of the alphanumeric code and enables continued refinement and expansion. A template table allows semantic definition, qualification, and linkage of concepts.

Semantic quality through semantic definition: refining the Read Codes through internal consistency

Checks of internal consistency in controlled medical vocabularies facilitate their development and assist refinement of the underlying terminological model. Two simple checks of consistency between knowledge in the subtype hierarchy and that in semantic definitions of concepts are described. It is proposed that these checks are a helpful adjunct to, but not a replacement for, large-scale involvement of domain experts in construction of controlled vocabularies.

Evaluating the terminology requirements to support multi-disciplinary diabetes care

Diabetes mellitus is a multi-system disease requiring lifetime multi-disciplinary care, which has proven individual and economic benefits. The delivery of service involves co-operation and communication between patient, carer and health care professionals, and systematic auditing of processes and outcomes. Sustained improvement necessitates regular data acquisition, aggregation and analysis. The terminology requirements to support patient-centred records and identified datasets are examined, and differences in purpose and scope highlighted. The many stakeholders involved in diabetes care have their own sublanguages and terminology requirements which need harmonising around a common core. The problems and solutions of accommodating these needs are explored in relation to the Read Thesaurus.

The Asian element in Australia: 1996

"There has been much public debate about the size of the Asian-born and Asian ethnic-origin population in Australia (unmixed). By combining these two elements, it is estimated that the total unmixed Asian component of Australia's population is 8.16 percent."

A comparison of a film-based and a direct digital dental radiographic system using a proximal caries model

OBJECTIVES

To compare the diagnostic accuracy of a dental radiographic film (Ektaspeed Plus) with the Sens-A-Ray direct digital imaging system using a proximal caries model. To study the effects of a scattering medium and compare the interpretations of dentists with dental students.

METHODS

We used 20 extracted premolar and molar teeth with 10 sound and 15 naturally carious surfaces, and prepared artificial cavities in the remaining 15 surfaces. Seven dentists and seven senior dental students reported the presence of lesions using a five point confidence scale. We analysed our data by Receiver Operating Characteristic (ROC) analysis and by obtaining sensitivities and specificities.

RESULTS

ROC areas showed no significant differences in the diagnostic accuracy achieved by dentists and dental students or by the addition of 20 mm of water as a scattering medium. A paler set of exposures produced significantly poorer diagnostic accuracy, but a darker set gave insignificant differences. Highly significant differences were found between the ROC areas for film and Sens-A-Ray and natural caries and artificial cavities, but the magnitudes of the differences were small. Sensitivities and specificities showed greater differences between methods and identified inferior interpretation of sound surfaces by students.

CONCLUSIONS

Film was superior to Sens-A-Ray in the interpretation of proximal caries. The effects of a scattering medium were insignificant or trivial. Students were less reliable than dentists in the interpretation of sound surfaces but performed equally well with respect to natural caries and artificial cavities.

The Read Thesaurus--creation and beyond

The creation of the Read Thesaurus was a unique undertaking, involving over 2000 clinicians. This clinically-led, multidisciplinary enterprise posed many organisational and professional challenges. The process of term collection and integration and the problems encountered are described. A brief account is given of the large task of maintenance and refinement. This paper looks at the practical and cultural aspects and describes how problems were tackled by good organisation, clear guidelines and much goodwill.

5-Azacytidine treatment of the fission yeast leads to cytotoxicity and cell cycle arrest

A fission yeast gene which shares considerable sequence homology with cytosine-specific DNA methyltransferases has recently been identified. This discovery has led us to investigate the effects of the treatment of fission yeast with the nucleoside analogue 5-azacytidine (5-azaC). 5-AzaC is known to inhibit cytosine methylation as a result of the formation of stable covalent complexes between DNA (cytosine-5) methyltransferases (C5 Mtases) and 5-azaC containing DNA. Here we demonstrate that 5-azaC treatment of Schizosaccharomyces pombe leads to reversible cell cycle arrest at the G2/M transition. This reversible arrest is dependent on the cell cycle checkpoint mechanisms which act to prevent the onset of mitosis in the presence of either damaged or unreplicated DNA. Treatment of S. pombe cell division cycle and checkpoint mutants indicates that 5-azaC causes DNA damage and is likely to inhibit a late stage in DNA replication. The data show that viability in the presence of the drug requires both the DNA damage and the replication checkpoint pathways to be functional. 5-AzaC also elicits a transcriptional response which is associated with DNA damage and the inhibition of DNA replication in fission yeast, and this response is absent in cells carrying G2 checkpoint mutations. The implications of these observations for both the use of 5-azaC in cancer chemotherapy and the existence of cytosine methylation in fission yeast are discussed.

Early increase in plasma parathyroid hormone levels following liver transplantation

BACKGROUND/AIMS

The pathogenesis of post-transplantation bone loss is poorly understood, although glucocorticoid therapy is believed to play an important role. In the present study we have measured plasma parathyroid hormone concentrations in the first few months after orthotopic liver transplantation, in order to examine the potential contribution of hyperparathyroidism to bone disease.

PATIENTS AND METHODS

Twenty-seven patients aged 32-54 years, 12 male, undergoing liver transplantation were studied prospectively before and for 3 months after operation. Plasma parathyroid hormone and serum 25-hydroxyvitamin D concentrations were measured by radioimmunoassay.

RESULTS

Plasma parathyroid hormone levels were normal in all but two patients prior to transplantation. There was a highly significant increase in plasma parathyroid hormone concentrations at 1 and 2 months (p < 0.0005 and 0.001, respectively, versus baseline); by 3 months, values were close to those obtained preoperatively. Serum 25-hydroxyvitamin D concentrations showed no significant change over the study period. However, 74% of the patients had subnormal values at baseline.

CONCLUSIONS

An early and transient increase in plasma parathyroid hormone after liver transplantation may be responsible for the high rates of bone loss which occur during the first few post-operative months. Prevention of post-transplantation bone disease is most likely to be achieved by peri-operative intervention with an anti-resorptive agent.

Functional anatomy of a common semantic system for words and pictures

The relationship between the semantic processing of words and of pictures is a matter of debate among cognitive scientists. We studied the functional anatomy of such processing by using positron-emission tomography (PET). We contrasted activity during two semantic tasks (probing knowledge of associations between concepts, and knowledge of the visual attributes of these concepts) and a baseline task (discrimination of physical stimulus size), performed either with words or with pictures. Modality-specific activations unrelated to semantic processing occurred in the left inferior parietal lobule for words, and the right middle occipital gyrus for pictures. A semantic network common to both words and pictures extended from the left superior occipital gyrus through the middle and inferior temporal cortex to the inferior frontal gyrus. A picture-specific activation related to semantic tasks occurred in the left posterior inferior temporal sulcus, and word-specific activations related to semantic tasks were localized to the left superior temporal sulcus, left anterior middle temporal gyrus, and left inferior frontal sulcus. Thus semantic tasks activate a distributed semantic processing system shared by both words and pictures, with a few specific areas differentially active for either words or pictures.

rTP: a candidate telomere protein that is associated with DNA replication

In this paper we describe the isolation and characterization of rTP, the replication Telomere Protein, formerly known as the telomere protein homolog. The rTP was initially identified because of its homology to the gene for the Oxytricha telomere-binding protein alpha-subunit. The protein encoded by the rTP gene has extensive amino acid sequence identity to the DNA-binding domain of the telomere-binding proteins from both Euplotes crassus and Oxytricha nova. We have now identified the protein encoded by the rTP gene and have shown that it differs from the telomere-binding protein in its abundance, solubility and intracellular location. To learn more about the function of rTP, we determined when during the Euplotes life cycle the gene is transcribed. The transcript was detectable only in nonstarved vegetative cells and during the final stages of macronuclear development. Since the peak transcript level coincided with the rounds of replication that take place toward the end of macronuclear development, it appeared that rTP might be involved in DNA replication. Immunolocalization experiments provided support for this hypothesis as antibodies to rTP specifically stain the replication bands. Replication bands are the sites of DNA replication in Euplotes macronuclei. Our results suggest that rTP may be a new telomere replication factor.

The genetics of the repair of 5-azacytidine-mediated DNA damage in the fission yeast Schizosaccharomyces pombe

We have recently demonstrated that Schizosaccharomyces pombe cells treated with the nucleoside analogue 5-azacytidine (5-azaC) require previously characterised G2 checkpoint mechanisms for survival. Here we present a survey of known DNA repair mutations which defines those genes required for survival in the presence of 5-azaC. Using a combination of single-mutant and epistasis analyses we find that the excision, mismatch and recombinational repair pathways are all required in some degree for the repair of 5-azaC-mediated DNA damage. There are distinct differences in the epistatic interactions of several of the repair mutations with respect to 5-azaC-mediated DNA damage relative to UV-mediated DNA damage.

412-positive mesodermal cells and the gonadal mesoderm are separate from the fat-cell lineage

The Drosophila retrotransposon, 412, is expressed in a cell-specific manner during embryogenesis. At stage 11, 412 transcripts are present in bilateral clusters of cells within the mesoderm. The posterior clusters of 412-positive cells become associated with the gonads at stage 13; however, the fate of the cells in the remaining clusters is unknown. We have tested by in situ hybridization to whole-mount embryos the possible identity of these cells with known precursor cell types present in bilateral clusters. We simultaneously located the 412-positive cells and the precursor cells to visceral muscle or the fat body. We have determined that the 412-positive cells do not correspond to these precursor cells and that the development of the visceral muscle or fat body does not affect the expression of 412 during embryogenesis.

Anatomical characterisation of surgical procedures in the Read Thesaurus

Each concept in the surgical operations chapter of the Read Thesaurus has been analysed to determine its anatomical site component. The underlying structure of this chapter and its relationship to the anatomy chapter are explored. The defined anatomical sites have been included as atomic maps in the Read Code template table, one of the key component files of the Thesaurus, relevant features of which are described. The analysis methodology is outlined and the value of an anatomically characterised surgical procedure terminology is discussed together with the implications of semantically defining a wider range of characteristics of surgical procedures.