PubMed Health⌕ Search

Biomedical subjects

R Hancock

Publications and source records attributed to R Hancock.

At least 37 records · Page 2Linked to original sources
PubMed1996

[The dual function of the proliferating cell nuclear antigen (PCNA) in the response of human cells to UV damages].

An auxiliary protein of DNA polymerases delta and epsilon, the proliferating cell nuclear antigen (PCNA), is necessary for efficient DNA replication in vivo and in vitro, and also for the repair synthesis in vitro, but its role in the excision repair of genome in vivo is not exactly established. In S-phase of unirradiated cells, PCNA is tightly bound to focal centers of DNA replication and is not removed by treatment with detergent Triton X-100, but is completely extracted from non-S-phase cells by the indicated detergent. It was shown earlier that after UV-irradiation PCNA could not be removed by the detergent even from non-S-phase cells. It was interpreted as the evidence of PCNA integration into the repair complex and of the participation of this protein in repair synthesis in vivo. In the present work the data were obtained indicating that the role of PCNA in cell response to UV-damage was not confined only to its possible involvement in repair synthesis. With the help of confocal microscopy it was established that in Triton X-100-extracted normal cells PCNA did not colocalize with the well known excision repair protein XPB/ERCC3, defective in cells from Xeroderma pigmentosum (complementation group B) patients. XPB-protein is induced by UV-irradiation in normal cells, and this induction is not observed in repair deficient cells. However, in such cells UV-light induces a detergent-resistant form of PCNA, and this form is obviously not connected with repair. It cannot be excluded that a rapid PCNA immobilization immediately after UV-irradiation of cells is needed for the facilitation of photochemical damage bypass during the subsequent replication of genome.

Adenocarcinoma↗
PubMed1996

Factors associated with nursing interventions to reduce incontinence in hospitalized older adults.

INTRODUCTION: The problem of incontinence in hospitalized elderly patients is rarely documented, and there is little research that determines why nurses choose to help or not help with this problem. Are hospital-based acute care nurses' attitudes and beliefs about incontinence associated with the perceived opportunity to assist the patient with the problem? What do hospital nurses know about causes and interventions relative to incontinence? METHODS: Two vignettes, one describing a patient with stress incontinence and one describing a patient with urge incontinence, were created. Questions measuring variables of a help-giving model were developed, and nurses were asked to mark on a Likert-type scale when answering each question. RESULTS: One hundred-fifty respondents returned completed questionnaires along with three nurse experts. Many hospital nurses believed incontinence was temporary and part of being old. As a group they had a more positive attitude toward intervening for urge incontinence and believed the physician and their nurse manager expected them to assist the patient with urge incontinence. Respondents tended to believe the patient was least likely to expect help. Respondents were evenly divided about opportunity to provide assistance for stress or urge incontinence. Less than half of the nurses correctly listed causes and interventions for stress or urge incontinence. CONCLUSIONS: Other clinical problems perceived as more pressing and lack of knowledge concerning appropriate helping measures affect nurses' perceptions of opportunity to intervene when elderly hospital patients are incontinent. Assessment and intervention are essential to quality nursing care. Undergraduate nursing education and ongoing staff education about incontinence are crucial if assessments and interventions are to be correct. Patients, as health care consumers, have to be more educated about incontinence and choose to have the problem addressed during hospitalization. The Agency for Health Care Policy and Research Clinical Practice Guidelines is a major recommended reference.

Aged↗
PubMed1995

Visualization of elementary DNA replication units in human nuclei corresponding in size to DNA loop domains.

Newly synthesized DNA in mammalian nuclei is concentrated in discrete nuclear granules called replication foci. These foci may be visualized using antibodies against 5-bromodeoxyuridine. In the early S-phase cells 100-250 foci are usually detected. On average, individual foci range between 0.5 and 2 microns in diameter and can be seen as clusters of more than ten average-sized (60-100 kb) synchronously activated replicons. In this study, employing minor modifications of the previous methods, we report the visualization of small replication foci of about 0.3 micron diameter (mini-foci). Some foci are clustered into folded chains consisting of 2-40 subunits. DNA content of one mini-focus is estimated to be 50-120 kb and there are 500-1500 mini-foci per cell in the early S-phase. Experimentally induced decrease in replicon size does not affect the size of mini-foci, suggesting that these represent elementary units of DNA replication in mammalian nuclei and are probably identical to the basic structural DNA loop domains.

Cell Line↗
PubMed1995

Functional and regulatory analysis of the OmpF-like porin, OpnP, of the symbiotic bacterium Xenorhabdus nematophilus.

The function and novel regulation of OpnP of the symbiotic/pathogenic bacterium, Xenorhabdus nematophilus was studied. In vitro pore-function analysis of purified OpnP indicated that the single-channel-conductance values were similar to that measured for the porin protein, OmpF, of Esherichia coli. Nucleotide sequence analysis revealed that the mature OpnP protein contained 348 amino acid residues and shared 55% amino acid sequence identity with OmpF. Similar to ompF, opnP mapped between asnS and aspC. The 16 transmembrane beta-sheet structures and the internal loop 3 were highly conserved, while the remaining external loop domains were more divergent. Primer extension analysis identified the start site of transcription of opnP. A sigma 70-type promoter, a perfect 20 bp OmpR-binding site, and a binding site for the antisense molecule, micF RNA, were found in the upstream region of opnP. While the overall sequence identity of the asn-opnP-aspC region was high, the intergenic region between asnS and opnP had diverged markedly. The asnS-opnP region was 313 bp shorter than the intergenic region between asnS and ompF and lacked the OmpR-binding site that is required for ompF repression by high osmolarity in E. coli. Results from osmolarity-shift experiments indicated that OpnP was not repressed by high osmolarity. It was also found that OpnP was thermally regulated.

Amino Acid Sequence↗
PubMed1995

Topoisomerase II as a target for anticancer chemotherapy.

Type II DNA topoisomerases are required for the segregation of genomic DNA at cell division in prokaryotic and eukaryotic cells, and inhibitors of these enzymes are potential cytotoxic agents in both prokaryotes and eukaryotes. The bacterial member of the topoisomerase II family, DNA gyrase, and the chemotherapeutic agents which target it are the subject of a recent review (Maxwell, A. et al., 1993, in Molecular Biology of DNA Topoisomerases, Andoh, T. et al., eds., pp. 21-30, CRC Press, Boca Raton). Here we present an overview of current knowledge of eukaryotic topoisomerase II and the anticancer agents which target this enzyme, focussing predominantly on new observations and recent reports and reviews.

Animals↗
PubMed1994

Correlation of cellular differentiation in human colorectal carcinoma and adenoma cell lines with metabolite profiles determined by 1H magnetic resonance spectroscopy.

The aim was to determine whether proton magnetic resonance spectroscopy (MRS) could grade human colorectal cells of differing malignant potential. A cell model of tumour development and progression comprising 2 non-tumorigenic adenoma lines and 4 carcinoma lines of increasing tumorigenicity was chosen. A gradual reduction in cellular differentiation and an accumulation of genetic alterations from adenoma to carcinoma characterized the selected cell lines. One-dimensional and 2-dimensional MRS showed that reduced differentiation in the cell model correlated with an increase in the levels of lipid, metabolites, the glycosylation intermediate uridine diphospho-N-acetylglucosamine and cell-surface fucosylation. Mutations involving the K-ras, APC and DCC genes are present both in adenoma- and in carcinoma-derived lines in this model, but the first evidence of an abnormality in the p53 gene was concomitant with the cells' ability to grow as a tumour in athymic nude mice. This genetic change coincided with the detection, by MRS, of UDP-hexose (ribose moiety, 2D MRS cross peak between H2 at 4.38 ppm and HI at 5.99 ppm) and the appearance of an additional fucosyl resonance (cross peak between-CH3 at 1.41 and H5 at 4.30 ppm) in the least tumorigenic of the carcinoma cell lines. An increase in complexity of the fucosylation spectral pattern was observed with further cellular de-differentiation and increased tumorigenicity. Collectively these data support the existence of an adenoma-carcinoma sequence.

Adenoma↗
PubMed1993

Localization of DNA topoisomerase II in Chinese hamster fibroblasts by confocal and electron microscopy.

The localization of the 170- and the 180-kDa isoforms of the enzyme DNA topoisomerase II in growing Chinese hamster fibroblasts has been studied by confocal immunofluorescence microscopy and immunogold electron microscopy after labeling with affinity-purified isoform-specific polyclonal antibodies. Immunofluorescence and immunogold studies, together with quantitative image analysis, show that the two isoforms are present in the nucleoplasm and in the nucleolus. In the nucleoplasm both isoforms are frequently localized at the periphery of heterochromatin regions. In the nucleolus the immunofluorescence and immunogold signals relative to surface area are higher than in the nucleoplasm; both isoforms are localized predominantly in the fibrillar zones. During mitosis both isoforms remain detectable in the cytoplasm. The differential expression of the two isoforms during the cell cycle, observed in other studies, suggests that they have different functions, and their presence in both the nucleoplasm and the nucleolus suggests that these functions are required in both of these nuclear compartments.

Animals↗
PubMed1993

An analysis of laryngoscope blade shape and design: new criteria for laryngoscope evaluation.

Laryngoscope blade design has tended to be relatively arbitrary and so far scientific analysis has not allowed useful comparisons between blade shapes. A new theoretical method of analysing laryngoscope blades is introduced and uses the depth of insertion profiles of two angular measurements. One represents eyeline displacement and the other the forward space that the blade occupies at the level of the mandible. Photographs of straight and curved blades were studied on Cartesian graphs with the tip T, at the origin and handle fittings parallel to the x-axis of the graph. Then, IT is any line from the origin to the incisor surface and represents a point of contact with the upper incisors for a given depth of blade insertion. Angle EIT (eyeline displacement) is to a tangent from I along the lower lingual surface of the blade. Point M is on the upper lingual surface of the blade, at right angles to IT, 1/3 of the distance from I along IT. Angle MIT (forward space) may be positive or negative depending on whether M is in front of or behind IT. The angles EIT, MIT and their additive combination are used in blade analysis. Negative MIT compensates for eyeline displacement as Macintosh size 3 and 4 blades have better combination scores than Miller size 3. All three are superior to the straight Soper size 3 blade. The Macintosh size 1 and 2 blades are quite different from the larger Macintosh blades. This theoretical basis for blade analysis is consistent with commonly expressed clinical opinions and may influence blade design in the future.

Equipment Design↗
PubMed1993

Proton MR and human cervical neoplasia: ex vivo spectroscopy allows distinction of invasive carcinoma of the cervix from carcinoma in situ and other preinvasive lesions.

The concept that high-resolution (8.5-T) hydrogen-1 magnetic resonance (MR) spectroscopy can be used as an adjunct to conventional histologic diagnosis of cervical neoplasia was investigated. Cervical biopsy specimens (n = 159) were examined with H-1 MR spectroscopy and the results compared with results of histopathologic analysis. A high-resolution lipid MR spectrum was observed in 39 of 40 invasive carcinomas, whereas the 119 preinvasive samples showed little or no lipid spectrum but were characterized by a strong unresolved resonance between 3.8 and 4.2 ppm. Peak ratios of the methylene/methyl and the unresolved/methylene resonances allowed accurate distinction between invasive and preinvasive epithelial malignancy (P < .0001). Since MR spectroscopic examination does not destroy the specimen, the specimens remained intact for further testing and histopathologic analysis. The authors conclude that H-1 MR spectroscopy can independently allow distinction between invasive and preinvasive lesions of the cervix and has the potential to assist in clinical management of cervical cancer.

Biopsy↗
PubMed1993

Malignancy-related characteristics of wild type and drug-resistant Chinese hamster ovary cells.

Chinese hamster ovary (CHO) cell lines are a very popular cell model for a wide range of studies but are often misused experimentally as a substitute for normal cells. Although CHO was originally derived from normal tissue, the cell lines studied here, including the parental wild type, have many characteristics which indicate that they have undergone malignant transformation. Biological properties associated with malignancy were investigated in this study on wild type CHO cells and 4 drug resistant sublines, EOT, Col R-22, Pod R11-6, and Vin R-1. We report evidence of tumorigenicity in experimental animals, invasive capacity, in vivo and in vitro, protease release by 2 of the cell lines, features related to drug resistance in the mutant sublines, and numerical and structural chromosomal abnormalities.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1993

Magnetic resonance spectroscopy detects cancer in draining lymph nodes.

The spread of cancer cells to draining lymph nodes is an important prognostic factor for many cancers and influences postoperative therapy in patients. Histopathology is used routinely to assess if lymph nodes contain metastases. There are, however, time and resource constraints on the volume of lymph node tissue that can be examined by the pathologist in a routine laboratory (less than 2% of each node), thus major sampling errors are possible. Conventional histopathology also relies on identifying aggregates of malignant cells for a positive diagnosis. Proton (1H) magnetic resonance (MR) spectroscopy can detect chemical changes, specifically increased levels of lactate, choline, fucose and amino acids, in lymph nodes infiltrated by cancer. Increase in lactate indicates the presence of anaerobically respiring cells, whereas choline reports that the cells are replicating. Since MR spectroscopy can identify early infiltration by malignant cells, before cell clusters are visible under the light microscope, it detects micrometastases in lymph nodes missed histopathologically. Furthermore, MR spectroscopy eliminates sampling errors since the entire lymph node is examined.

Adenocarcinoma↗
PubMed1992

Evaluation of an in vitro invasion assay for use on solid tissue samples and cultured cells.

An invasion assay, developed for monitoring the in vitro penetration of reconstituted basement membrane, matrigel, was modified and successfully applied to solid tumours, normal tissues as well as a variety of normal and tumour cell lines. However, we found that some normal fibroblasts were capable of in vitro invasion whilst some malignant cell lines with invasive capacity in vivo did not penetrate the matrigel. Nevertheless, this method can distinguish invasive capacity within a tumour model, and as a consequence may be used to elucidate some of the biochemical mechanisms in the invasion process comparing cells grown both in vitro and in vivo. Since the method does not always correlate with invasion in vivo the results must be interpreted with caution.

3T3 Cells↗
PubMed1991

Precise localization of the alpha-globin gene cluster within one of the 20- to 300-kilobase DNA fragments released by cleavage of chicken chromosomal DNA at topoisomerase II sites in vivo: evidence that the fragments are DNA loops or domains.

We have mapped the position of the alpha-globin gene cluster in the 20- to 300-kilobase fragments of chromosomal DNA isolated from growing chicken HD3 erythroblastoid cells exposed to 4'-demethylepipodophyllotoxinthenylidene beta-D-glucoside. This epipodophyllotoxin traps functioning topoisomerase II molecules, the denaturation of which cleaves DNA and reveals their reaction sites. The DNA fragments, prepared by centrifugation in sucrose gradients, bind selectively to glass-fiber filters and are protected from lambda 5'-exonuclease, properties compatible with the presence of a topoisomerase II subunit bound to their 5' ends. Restriction enzyme cleavage of the fragments and hybridization with cloned alpha-globin-region probes reveal additional distinctive bands not seen in control DNA, allowing the localization of fragment ends near this gene cluster. The terminal regions of fragments from sucrose gradients or from field-inversion electrophoresis gels were also used to probe cloned regions of the gene cluster. Both approaches show that this cluster of three genes, which is not expressed in these cells, is located at a specific position in a approximately 20-kilobase DNA fragment. The upstream end of this fragment lies in a region that contains a site of DNA attachment to the nuclear matrix mapped by both in vivo and in vitro methods, and its downstream end is flanked by approximately 80% A + T sequences characteristic of matrix-attachment regions. These observations suggest that the DNA fragments are formed because topoisomerase II molecules can specifically and readily integrate into DNA at matrix-attachment regions and that the fragments represent entire DNA loops or domains.

Animals↗
PubMed1991

Nuclear matrix attachment regions and topoisomerase II binding and reaction sites in the vicinity of a chicken DNA replication origin.

We have mapped nuclear matrix attachment regions (MARs), defined by their specific binding to nuclear matrices in vitro, and sites of topoisomerase II reaction, detected by DNA cleavage in vitro in the presence of the inhibitor VM-26, in the vicinity of the replication origin of the chicken alpha-globin gene domain. Two MARs are located close to the downstream end (in the direction of transcription) of a 3 kb fragment which includes the origin. These MARs contain sites for strong topoisomerase II binding and reaction. Our observations on this gene domain support two hypotheses concerning MARs in eukaryotic cells, namely that they are close to DNA replication origins and that they contain multiple topoisomerase II recognition sites.

Animals↗