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Biomedical subjects

C Price

Publications and source records attributed to C Price.

At least 127 records · Page 7Linked to original sources
PubMed1992

The HsdS polypeptide of the type IC restriction enzyme EcoR124 is a sequence-specific DNA-binding protein.

The HsdS and HsdM polypeptides of the type IC restriction enzyme EcoR124 have been purified independently and used in a set of gel retardation experiments to determine the minimum requirements for sequence-specific recognition of DNA by this enzyme. The HsdS polypeptide alone is able to bind to DNA in a sequence-specific manner. In addition, whilst the presence of the HsdM polypeptide gives rise to a stimulation of DNA binding by the HsdS subunit it is not clear whether, under the conditions of the experiments reported here, the HsdS subunit maintains the same interactions with the HsdM subunits observed in the absence of DNA.

Bacterial Proteins↗
PubMed1992

Diagnosis of cytomegalovirus infection in heart transplant recipients.

In a prospective study eight (47%) heart transplant recipients had recurrent cytomegalovirus (CMV) infection. Of these, five had received hearts from seropositive donors. Neither serology nor virus isolation from urine was reliably associated with clinical CMV infection, but a high CMV IgM index correlated with CMV infection.

Antibodies, Viral↗
PubMed1992

Effects of niobium filtration and constant potential on image quality in dental radiography. 2. Objective assessment.

The effects of niobium filtration and constant potential on image quality were explored by asking observers to identify numbers of circular areas of small density differences in zones of high and low density. Successful identification was related negatively to half-value layer. This relationship was particularly strong in the case of self-rectified units without additional niobium filtration and the constant potential units (r2 = 0.994, P < 0.0005). Constant potential had no effect other than in relation to half-value layer. Additional niobium filtration detracted from successful identification, but slightly less than would be predicted by the half-value layer. Whether this difference is significant or relevant has not been established. The findings of this study, in conjunction with our previous investigations, have failed to demonstrate any clear indications for preferring constant potential supply over self-rectification or for using niobium as an additional filter material. Half-value layer has been shown to be a reliable indicator of the effects of beam quality on emulsion speed, attenuation in water, and image quality. It appears that the methods employed to change the beam quality have no specific effects.

Filtration↗
PubMed1992

Effects of additional filtration on image quality in dental radiography: comparison of niobium with aluminium.

Niobium filtration was compared with additional aluminium filtration with respect to the image quality of dental radiographs. An aluminium phantom was constructed which produced densities similar to those found in periapical regions and in enamel. Eight beam qualities were investigated and objective evaluation of the films was made by 20 observers with respect to any effects on radiographic contrast and successful identification of a pattern of holes in the phantom. Radiographic contrast decreased linearly as the half-value layer increased (r2 = 0.960, P < 0.0005), confirming the negative relationship between contrast and half-value layer as previously shown. No specific effect of niobium filtration on radiographic contrast was demonstrated. The number of successful identifications decreased with increasing half-value layer. A regression analysis in the total and dark zones yielded r2 values of 0.937 and 0.943 (P < 0.0005). Similar analyses for both the light and overall zones showed weaker relationships (r2 = 0.734 and 0.742: P = 0.007 and 0.006 respectively). Niobium reduces successful identification to the same extent as equivalent aluminium filtration.

Aluminum↗
PubMed1992

Three-dimensional reconstruction of magnetic resonance images of the temporomandibular joint by I-DEAS.

Evaluation of the temporomandibular joint has been limited by the inability of current technology to image complex morphology and motion in three dimensions. An engineering design program, I-DEAS, has been used to construct solid models from magnetic resonance images. A dried skull with an acrylic resin temporomandibular disc replica, immersed in water, provided sagittal and coronal MR images. Linear dimensions and disc volumes obtained from the models were compared with the original and found to be consistent, within the limits imposed by the slice thickness. We have applied the method to the living joint in an asymptomatic volunteer, and report our initial experience in demonstrating the spatial relationships and motion of the joint components.

Humans↗
PubMed1991

A general approach to the isolation of cell cycle-regulated genes in the budding yeast, Saccharomyces cerevisiae.

We describe a general approach to the isolation of cell cycle-dependently regulated transcripts in Saccharomyces cerevisiae. This approach is based on the physical identification of cell cycle-regulated transcripts by Northern hybridization using as probes yeast DNA isolated from an ordered S. cerevisiae genomic library. The purpose of this is twofold; first, to assess the importance of transcriptional regulation in cell cycle control; and second, to identify novel genes that may have important roles in the eukaryotic cell cycle. We report the isolation of two previously uncharacterized genes that are transcribed at points in the cell cycle to which specific transcriptional activation has not been assigned: namely, mitosis and early G1 phase. It is argued that these transcripts serve as important landmarks for cell cycle events that are not readily distinguished by either morphological or cytological criteria. The cell cycle-dependent transcription of the RNR1 and CLN1 genes is also described and the implications for cell cycle control, in G1, are discussed with reference to these two genes.

Blotting, Northern↗
PubMed1991

The role of CDC28 and cyclins during mitosis in the budding yeast S. cerevisiae.

cdc28-1N is a conditional allele that has normal G1 (Start) function but confers a mitotic defect. We have isolated seven genes that in high dosage suppress the growth defect of cdc28-1N cells but not of Start-defective cdc28-4 cells. Three of these (CLB1, CLB2, and CLB4) encode proteins strongly homologous to G2-specific B-type cyclins. Another gene, CLB3, was cloned using PCR, CLB1 and CLB2 encode a pair of closely related proteins; CLB3 and CLB4 encode a second pair. Neither CLB1 nor CLB2 is essential; however, disruption of both is lethal and causes a mitotic defect. Furthermore, the double mutant cdc28-1N clb2::LEU2 is nonviable, whereas cdc28-4 clb2::LEU2 is viable, suggesting that the cdc28-1N protein may be defective in its interaction with B-type cyclins. Our results are consistent with CDC28 function being required in both G1 and mitosis. Its mitotic role, we believe, involves interaction with a family of at least four G2-specific cyclins.

Alleles↗
PubMed1991

Direct sequence analysis of 14q+ and 18q- chromosome junctions at the MBR and MCR revealing clustering within the MBR in follicular lymphoma.

The t(14;18) translocation is a highly consistent feature of follicular lymphoma although the underlying mechanism generating this fusion remains uncertain. The breakpoints on chromosome 18 are at one of two sites, designated mbr and mcr, in the bcl-2 gene. A polymerase chain reaction strategy has been developed for amplification and direct sequencing of the resultant 14q+ and 18q- reciprocal junctions. Sequence analysis of the amplified 14q+ junction established that 21 tumours contained a bcl-2 (mbr) sequence to an immunoglobulin JH region, the majority being J5 or J6. A nonrandom pattern of breakpoints within the mbr region was found. Clustering of the breakpoint occurred with over 60% of the translocations clustering within 10 bases. There was a second cluster within the mbr 50 bases 3' of the first cluster. One of these junctions had an unusual configuration with the bcl-2 and JH sequences separated by a recognisable DH region. This suggests that at least some of the junctional sequences, previously thought of as N insertions, may be fragments of unrecognised DH regions. In one of these tumours it was possible to sequence the reciprocal 18q- junction, showing it to consist of a DH/bcl-2 (mbr) fusion. Analysis of both reciprocal junctions for a translocation in the mcr region of bcl-2, showed that this 18q- junction also consisted of DH fused to a bcl-2 sequence. In contrast to previous analyses, which demonstrated either loss or duplication of bcl-2 sequences at the breakpoints, the bcl-2 sequence was conserved during the mbr and mcr translocations in this study.(ABSTRACT TRUNCATED AT 250 WORDS)

Base Sequence↗
PubMed1991

Effects of niobium filtration and constant potential on the sensitometric responses of dental radiographic films.

Two half-wave self-rectified dental X-ray units and two constant potential units were compared with respect to the sensitometric properties of D- and E-speed emulsions. The effects of additional niobium filtration on the half-wave beams were explored. Important differences between the responses of the two emulsions identified inadequacies in the International Standards method for determining film speed. The constant potential units gave values of speed within the range of the half-wave rectified units. Additional niobium caused an increase in the film speed produced by the half-wave units, especially in the case of the lower kilovoltage, less filtered beam. For all beam qualities investigated, the film speed was related to the half value layer. No specific effects of the constant potential supply, nor of the niobium filtration were identified. Film contrast was unrelated to beam quality, and differed in several respects between the two emulsions.

Filtration↗
PubMed1991

Effects of niobium filtration and constant potential on the attenuation of dental X-ray beams by water.

Two half-wave, self-rectified dental X-ray units and two constant potential units were compared with respect to the attenuation of the X-ray beams by water. The effect of additional niobium filtration on the half-wave beams was also explored. Exposures were standardized to give the same values at a depth of 2 cm. The constant potential units gave values of relative exposure which fell within the range of exposures produced by conventional half-wave, self-rectified units. The addition of niobium as a filter material resulted in a reduction of surface exposure of between 10% and 12%, depending on the beam quality. The more penetrating beams resulted in relatively smaller exposure at the surface and gave relatively greater exposure at deeper levels. The addition of niobium resulted in an increase in relative exposure of 30.6% at 70 kVp and 10.7% at 90 kVp at a depth of 6 cm. There was a linear relationship between relative exposure and half-value layer, both at the surface and at a depth of 6 cm. Regression analysis yielded r2 values of 0.925 at the surface and 0.919 at 6 cm (P less than 0.0005). This study has failed to show differences in attenuation due to niobium filtration and constant potential, other than might be expected from half-value layer.

Filtration↗
PubMed1991

Effects of niobium filtration and constant potential on image quality in dental radiography. 1: Subjective assessment and contrast.

Two half-wave, self-rectified dental X-ray units and two constant potential units were compared with respect to the image quality of dental radiographs, and the effect of additional niobium filtration on the half-wave beams was explored. Eight beam qualities were investigated and subjective assessments of the films were made by 20 observers. An aluminium phantom was constructed which produced densities similar to those found on dental radiographs in periapical regions and in enamel. The effect of beam quality on the radiographic contrast between these densities was studied. Subjectively, there was a preference for the softer beams and for films in the middle range of exposures. The addition of niobium reduced preference by 50% at both 70 and 90 kVp. With one exception, the constant potential units fell within the range of preferences recorded for the self-rectified units. However, the relationship of preference to half-value layer was not significant. Radiographic contrast decreased linearly as the half-value layer increased (r2 = 0.956, P less than 0.0005), and no specific effects of constant potential or niobium filtration were revealed.

Evaluation Studies as Topic↗
PubMed1991

Case study. ESRD after living-related donation.

The patient met three of the four expected outcomes. He has in the past and is currently making informed decisions. reguarding his health care. Momentarily, he is demonstrating effective, positive coping strategies and problem-solving techniques. However, the fourth, and probably most critical outcome, is not being met. A.J. has not remained free of complications secondary to his kidney donation. It is estimated that he is facing ESRD, and all related medical and nursing regimens in less than 1 year. Additionally related to his elective nephrectomy, he will experience the loss of his 12-year military career and associated benefits. Although the nursing interventions were instrumental in assisting A.J. and his wife to cope with his acute situation, they now face the fears and anxieties of lifetime chronic illness. Theoretically, this patient may have experienced chronic renal failure at some point in his life, but the nursing intervention could have been approached as a pre-ESRD patient, in lieu of his status as a postliving related donor patient.

Adaptation, Psychological↗
PubMed1990

Direct sequence analysis of the 14q+ and 18q- chromosome junctions in follicular lymphoma.

Although the t(14;18) chromosome translocation has been demonstrated to be a highly consistent feature of follicular lymphomas, the underlying mechanism generating this fusion has remained uncertain. To examine this question further, a polymerase chain reaction strategy has been devised to permit the amplification and direct sequencing of the resultant 14q+ and 18q- reciprocal junctions. Direct sequence analysis of amplified 14q+ junctions established that 7 of 11 tumors contained a bcl-2 (mbr) sequence fused to an immunoglobulin JH region (five were J6 and two were J5). One of these junctions had an unusual configuration with the bcl-2 and JH sequences separated by a recognizable DH region. This finding suggests that at least some of the junctional sequences, previously thought of as N insertions, may be fragments of unrecognized DH regions. It was also possible to amplify and sequence 18q- junctions using a primer based on the DH recombination signal sequences. Several 18q- junctions were shown to consist of DH/bcl-2 (either mbr or mcr) fusions. In two tumors the 14q+ and 18q- junctions were fully sequenced, and it was demonstrated that the bcl-2 sequence was conserved during mbr and mcr translocations. This contrasts with previous analyses that demonstrated either loss or duplication of several bases at the breakpoints in the bcl-2 gene.

Base Sequence↗