Biomedical subjects

K Davidson

Publications and source records attributed to K Davidson.

At least 55 records · Page 3Linked to original sources

PubMed1999

Elimination of extrachromosomal c-myc genes by hydroxyurea induces apoptosis.

Hydroxyurea (HU) increases extrachromosomal DNA elimination in tumor cell lines. The c-myc oncogene is one of the many relevant amplified genes contained within the extrachromosomal DNA compartment. Spontaneous loss of amplified copies of c-myc induces terminal differentiation and apoptosis in the human HL-60 leukemia cell lines. In the present study, we evaluate HU's ability to induce apoptosis by eliminating extrachromosomally located c-myc oncogene in human tumor cell lines. The consequences of eliminating extrachromosomal DNA by HU were explored in two different cell lines using the TdT assay and acridine orange/ethidium bromide labeling. COLO 320 clone 3 and COLO 320 clone 21 cell lines contain the same number of amplified copies of c-myc oncogene, but located respectively on extrachromosomal DNA, and intrachromosomally in homogeneously staining regions. HU induced apoptosis in the COLO 320 clone 3 cell line by a time and concentration dependent mechanism but could not induce apoptosis in the COLO 320 clone 21 cell line. These results suggested that HU-induced apoptosis in COLO 320 cell lines depends on elimination of extrachromosomal amplified copies of the c-myc oncogene. The ability of HU to eliminate extrachromosomally amplified copies of the c-myc oncogene and to induce apoptosis should be considered when targeting malignancies with amplification of the c-myc oncogene in an extrachromosomal site.

Journal Article↗

PubMed1999

The short-term effects of a hostility-reduction intervention on male coronary heart disease patients.

This preliminary study examined the effects of a hostility-reduction intervention on patients with coronary heart disease (CHD). Twenty-two high-hostile CHD men were matched on age and hostility and then randomly assigned to a hostility intervention (N = 10) or an information-control group (N = 12). Patients were reassessed immediately and 2 months posttreatment on hostility (with self-report and structured interview) and resting blood pressure. The intervention's overall effect size was moderately strong (d' = .62). Intervention patients reported at both reassessments and were observed at follow-up to be less hostile than controls. At follow-up, intervention patients had significantly lower diastolic blood pressure (DBP) than controls. Finally, reductions in hostility were significantly and positively correlated with reductions in DBP. Replication with a larger sample and CHD outcomes is recommended.

Adult↗

PubMed1999

A human breast cancer model for the study of telomerase inhibitors based on a new biotinylated-primer extension assay.

Telomerase is an RNA-dependent polymerase that synthesizes telomeric DNA (TTAGGG)n repeats. The overall goal of our work was to establish human cancer models that can be used to design clinical trials with telomerase inhibitors. The objectives of this study were (1) to set up a human breast cancer system that allows evaluation of the effects of telomerase inhibitors in cultured cells using a non-amplified telomerase assay and (2) to test this system using two drugs (cisplatin and TMPyP4) that affect the telomerase expression in breast cancer cells in culture. We first compared the telomerase activity in a variety of human breast cancer cell lines to that of other tumour types using a new biotinylated-primer extension assay. Our method, based on a non-amplified primer extension assay shows the direct incorporation of 32P-labelled nucleotides induced by telomerase on human telomeric primers. The 32P-dGTP labelled telomerase-extended 5'-biotinylated (TTAGGG)3 primer can subsequently be separated using streptavidin-coated magnetic beads. As compared to other non-amplified method, we showed that this procedure improved the characterization and the quantification of the banding pattern resulting from telomerase extension by reducing the radioactive background. Using this method, we observed that telomerase activity varies markedly in a panel of 39 human cancer cell lines. For example, MCF7 breast cancer cells in culture showed intermediate telomerase activity corresponding to 33.8+/-3.4% of that of the HeLa cells (reference cell line). Similarly, the telomere length varied with each cell line (average: 6.24+/-6.16). No correlation between the level of telomerase and telomere length was observed, suggesting that a high processivity is not required to maintain telomeres and that, in some cell lines, another mechanism of telomere elongation can maintain telomere length. From this study, we selected MCF7 and MX1 models that showed reproducible telomerase activity and a relatively limited telomere length for the testing of potential telomere-telomerase interacting agents. Using cisplatin and a new porphyrin-derived compound TMPyP4, we showed that our model was able to detect a down-regulation of the telomerase activity in MCF7 cells in culture and in a human MX1 tumour xenografts. Based on these results, a breast cancer model for evaluating telomerase and telomere interactive agents is proposed.

Animals↗

PubMed1999

Locally advanced breast cancer: the outcome of primary polychemotherapy based on infusional 5 fluorouracil.

Over a 5-year period, 75 patients with locally advanced breast cancer presenting to the Edinburgh Breast Unit were managed with a policy of infusional primary chemotherapy. For 65 patients, the regimens comprised infusional 5 fluorouracil with anthracycline and/or either cyclophosphamide or cisplatinum (AcF, CAF or ECF) whilst 10 older patients had CMF-inf. The overall activity and tolerability for the regimens was good with a 76% objective response rate including 15% clinical complete responses. Surgery was possible in 64% and pathological complete responses confirmed in 7 (9.3%). Median disease free survival (DFS) is 5.23 years. Factors predicting for DFS or Overall Survival (OS) were assessed in this small group and ER positive patients did better than ER negative although there was surprisingly no negative DFS or OS association with inflammatory disease or advancing age. We found a paradoxical interaction with use of post-chemotherapy tamoxifen which was significantly associated with poorer DFS and OS overall and in the ER negative subgroups.

Journal Article↗

PubMed1999

Language plus for international graduate students in nursing.

PURPOSE: To provide information about an English-language support program that focuses on the needs of international graduate nursing students. The growing presence of these students coincides with the increasing numbers of universities committed to world health. Crucial social and language competence affect the success and progress of international students in graduate nursing programs. DESIGN: Reviewed literature was 1980 to 1998, in nursing and applied linguistic research including second-language acquisition, phonology, discourse analysis, and language pragmatics to identify social and language phenomena. FINDINGS: Investigators suggest essential elements such as conventions of academic writing, reading comprehension, vocabulary, and pronunciation skills be included in the supportive Language Plus program. CONCLUSIONS: Ongoing development of the Language Plus program can promote collaboration between nurses and linguists and increase the success of international graduate nursing students.

Communication Barriers↗

PubMed1999

Increasing constructive anger verbal behavior decreases resting blood pressure: a secondary analysis of a randomized controlled hostility intervention.

We hypothesized that increasing anger verbal behavior in an assertive, constructively motivated style should decrease resting blood pressure (BP) and that this behavior may be one mechanism through which hostility relates to BP. We tested this hypothesis by conducting secondary analyses on a single-blind, matched, randomized controlled study of hostility modification and BP. A total of 22 high-hostile male patients with coronary heart disease were matched on age and hostility level and were randomly assigned to either an 8-week cognitive-behavioral hostility treatment (n = 10) or an information-control group (n = 12). Patients were reassessed after treatment and at 2-month follow-up on hostility, observed anger expression, and resting BP. We found that decreases in hostility predicted increases in constructive anger behavior-verbal component, which in turn predicted decreases in resting BP at follow-up. Thus, one of the mechanisms underlying the hostility-BP association may be the lack of constructive anger expression.

Journal Article↗

PubMed1999

Ultrastructural and protein analysis of surfactant in the Australian lungfish Neoceratodus forsteri: evidence for conservation of composition for 300 million years.

The Australian lungfish Neoceratodus forsteri is the most primitive member of the lungfish family, with a surfactant lipid composition similar to the actinopterygiian fishes, which evolved 400 million years ago. We have analysed the proteins associated with surfactant isolated from lung lavage of this species, and used electron microscopy and immunohistochemistry to examine the surfactant structures and the subcellular localisation of these proteins. The epithelial lining of the gas-exchange region of the lungfish lung consists of one basic cell type, which has characteristics of both mammalian alveolar type I and type II cells and may be the common ancestor of both. It has long cytoplasmic plates containing microvilli, large osmiophilic bodies resembling mammalian lamellar bodies and a cytoplasm rich in metabolic organelles. Extracellular structures reminiscent of mammalian surfactant forms, but not including tubular myelin, were observed in the airspaces. Immunochemical analysis of the lungfish surfactant and lung tissue, using antibodies to human SP-A and SP-B, showed a similar staining pattern to human surfactant, indicating that SP-A- and SP-B-like proteins are present. Immunohistochemistry revealed that both SP-A and SP-B reactivity was present in the secretory cell osmiophilic bodies. In conclusion, our results suggest that, despite the great diversity in present day lung structures, a common cellular mechanism may have evolved to overcome fundamental problems associated with air-breathing.

Animals↗

PubMed1999

Appendix: education and information resources in hyperbaric medicine.

A comprehensive listing of hyperbaric medicine resources is provided. These resources serve the educational and information needs of those who wish to enter this medical specialty, as well as those who practice it. A selected hyperbaric specific bibliography is included, as is the methodology to stay current with the scientific and technological advances of this field.

Humans↗

PubMed1998

Dimethyl sulfoxide (DMSO) causes a reversible inhibition of telomerase activity in a Burkitt lymphoma cell line.

INTRODUCTION: Telomerase is an enzyme that is required for maintenance of telomeres. This enzyme has been shown to be present in germline tissues and majority of tumors and tumor cell lines. The regulation of telomerase is an area of active investigation in different models because, potentially, inhibition of this enzyme could be important in cancer therapy. To study the regulation of this enzyme in lymphoma cell lines, we used DMSO to produce a reversible G0/G1 arrest in Raji cell line, as shown earlier [Sawai M, Takase K, Teraoka H, Tsukada K. Reversible G1 arrest in the cell cycle of human lymphoid cell lines by dimethyl sulphoxide. Exp Cell Res 1990;187:4-10]. METHODS: In this study, we use a highly quantifiable conventional (non-amplified) assay to study the effect of DMSO on telomerase. In addition, we studied cellular proliferation and cell cycle profiles of the cells treated and, subsequently, released from DMSO induced blockage. RESULTS: In this model, DMSO reversibly inhibited telomerase activity that could be restored after release from the blockage. The inhibition of telomerase seems to parallel cellular proliferation and it appears that telomerase is regulated upon entry into the cell cycle. This view is consistent with other previously published views on relationship of telomerase with exit from cell cycle. CONCLUSION: Our observations demonstrate a novel effect of DMSO on cellular mechanisms in Raji cell line. It may provide an attractive model to further study regulation of telomerase in this cell line.

Burkitt Lymphoma↗

PubMed1998

Activity of (-)-2'-deoxy-3'-oxacytidine (BCH-4556) against human tumor colony-forming units.

BACKGROUND: BCH-4556 ((-)-2'-deoxy-3'-oxacytidine) is an L-nucleoside analogue shown to have broad preclinical anti-cancer activity, particularly against solid neoplasms such as prostate, renal, and hepatoma in vitro and in vivo, in contrast to cytosine arabinoside (ara-C) which is preferentially active against leukemia. MATERIALS AND METHODS: The antitumor activity of BCH-4556 was evaluated using human tumor colony-forming unit (HTCFU) assay, in which fresh tumor specimens were taken directly from patients with and without prior chemotherapy. RESULTS: Overall, in vitro responses (50% or less survival compared to untreated controls) were observed in 11% (two of 18), 29% (five of 17) and 50% (nine of 18) of specimens treated for one hour with BCH-4556 at 1, 10 and 100 micrograms/ml, respectively; and 16% (nine of 55), 32% (24 of 74), 48% (35 of 73) and 65% (11 of 17) of specimens treated continuously with BCH-4556 at 0.1, 1, 10 and 100 micrograms/ml, respectively. With the one-hour schedule, a significant difference in response rates was noted between 100 micrograms/ml and 1 microgram/ml (P = 0.02). With the continuous schedule, significant differences in response rates were observed between 1 microgram/ml and 0.1 microgram/ml (P = 0.02), between 10 micrograms/ml and 0.1 microgram/ml (P = 0.0001), as well as between 10 micrograms/ml and 1 microgram/ml (P = 0.01). A trend suggesting the superiority of continuous exposure was observed in paired specimens (n = 18) at comparable drug concentrations. Activity was noted against ovarian (nine of 16 = 56%), renal (three of four = 75%), and melanoma (two of two = 100%) HTCFU at 10 micrograms/ml using the continuous schedule. Comparisons between BCH-4556 and paclitaxel were made in 32 specimens at 10 micrograms/ml using the continuous exposure. Twenty-three specimens showed similar responses with both drugs; seven showed better responses with BCH-4556; and two showed better responses with paclitaxel (P = 0.18). CONCLUSIONS: Promising activity was observed with BCH-4556 against ovarian, renal, and melanoma HTCFU. There appeared to be a positive relationship between BCH-4556 concentration and response using both one-hour and continuous exposures. Continuous exposure to BCH-4556 provided high response rates especially at concentrations above 10 micrograms/ml. For both one-hour and continuous exposures, BCH-4556 had similar, and at times, greater potency than paclitaxel against the same tumor specimens in the present study.

Antineoplastic Agents↗

PubMed1998

Bioavailability of phylloquinone from an intravenous lipid emulsion.

This randomized, controlled study evaluated the bioavailability of phylloquinone from an intravenous lipid emulsion. A mild vitamin K deficiency was induced in 12 healthy adult men and women by dietary restriction of phylloquinone (40 microg/d, days 1-11) and by administration of warfarin (1.0 mg/d, days 5-11). On day 11, subjects received a 500-mL intravenous solution of either lipid or saline, both of which contained 154 microg phylloquinone. Bioavailability was assessed by serial measurements of plasma phylloquinone, vitamin K1-2,3-epoxide. PIVKA-II (proteins induced by vitamin K absence or antagonists-II), and percentage undercarboxylated osteocalcin. As a result of vitamin K deficiency and minidose warfarin, vitamin K1-2,3-epoxide, PIVKA-II, and percentage undercarboxylated osteocalcin increased significantly between days 1 and 11 (P = 0.05, 0.016, and 0.001, respectively). With the infusions, plasma phylloquinone increased in both groups (P = 0.001). After the infusions vitamin K,-2,3-epoxide decreased in both groups (P = 0.002). Changes in plasma phylloquinone and vitamin K1-2,3-epoxide were no different in the two groups (mean areas under the curves +/- SEM: 116+/-13 nmol x h/L for the saline group and 102+/-20 nmol x h/L for the lipid group for phylloquinone; 38.6+/-7.5 nmol x h/L for the saline group and 31.3+/-9.0 nmol x h/L for the lipid group for vitamin K1-2,3-epoxide). PIVKA-II decreased significantly from baseline values (P = 0.005) in both groups after the infusions. Intravenous lipid reversed the effects of minidose warfarin and of dietary restriction of phylloquinone on hemostasis and vitamin K nutritional status. This reversal was no different from that seen with the infusion of phylloquinone in a saline solution.

Adult↗

PubMed1998

Mitoguazone induces apoptosis via a p53-independent mechanism.

Mitoguazone (methylglyoxal bisguanylhydrazone, methyl-GAG or MGBG) is a synthetic polycarbonyl derivative with activity in patients with Hodgkin's and non-Hodgkin's lymphoma, head and neck cancer, prostate cancer, and esophageal cancer. Mitoguazone has also recently been documented to have activity in patients with AIDS-related lymphoma. Among anticancer drugs, mitoguazone has a unique mechanism of action via interference with the polyamine biosynthetic pathway. Polyamines stabilize DNA structure by non-covalent cross-bridging between phosphate groups on opposite strands. In addition, mitoguazone causes uncoupling of oxidative phosphorylation. In this study, the ability of mitoguazone to induce apoptosis by inhibiting the polyamine pathway was assessed in three Burkitt's lymphoma cell lines (Raji, Ramos and Daudi) and one prostate carcinoma cell line (MPC 3). Additional evaluations were performed in two human breast cancer cell lines (MCF7 with wild-type p53 and VM4K with mutated p53) to determine whether the p53 tumor suppressor gene was required for efficient apoptosis induction. The present study demonstrated that mitoguazone induces apoptosis in all the different human cancer cell lines tested in a concentration- and time-dependent way, and triggers a p53-independent programmed cell death in the human breast cancer MCF7 cell line.

Antineoplastic Agents↗

PubMed1998

Respiratory mechanics and surfactant in the acute respiratory distress syndrome.

1. Although abnormalities in pulmonary surfactant were initially implicated in the pathogenesis of the acute respiratory distress syndrome (ARDS) 30 years ago, most subsequent research has focused on mediators of the parenchymal acute lung injury (ALI) and the associated increase in alveolocapillary permeability. 2. Surfactant is essential for normal breathing and the severity of ALI correlates with surfactant dysfunction and abnormalities in surfactant composition; however, no relationship has been shown with respiratory system compliance. In neonates and most animal models, respiratory system compliance will directly reflect the elastic properties of the lung. However, the greater vertical height of the chest wall in adults, in combination with the increase in lung density due to ALI, results in dependent collapse of alveoli. Because simple, global measurement of compliance is strongly influenced by the volume of aerated lung, alternative measures of respiratory mechanics may reflect surfactant dysfunction. 3. Using a dynamic, volume-dependent model of respiratory mechanics to indirectly reflect this heterogeneous inflation, we have found direct relationships with surfactant composition in patients with ARDS. A failure of surfactant to increase surface tension in large alveoli may also explain why lung overdistension occurs at relatively low pressures. Furthermore, surfactant dysfunction will exaggerate heterogeneous lung inflation, augmenting regional overinflation, and is essential for ALI secondary to repetitive opening and closing of alveoli during tidal ventilation. 4. Ventilation-induced ALI has also been shown to result in massive increases in pro-inflammatory cytokines within the lung. Because ALI itself fails to compartmentalize cytokines, with spillover into the systemic circulation resulting in distant organ dysfunction, surfactant dysfunction may have widespread implications.

Adult↗

PubMed1998

Recovery of positive future thinking within a high-risk parasuicide group: results from a pilot randomized controlled trial.

OBJECTIVES: The research examined: (i) whether high risk parasuicide patients showed a deficit in positive future thinking but no increase in negative future thinking; and (ii) whether such a deficit could be remedied by a brief, manual-assisted psychological intervention (manual assisted cognitive-behaviour therapy; MACT). DESIGN: A cross-sectional, mixed model design was used to assess differences between a sample of high risk parasuicide patients and matched controls on future thinking. A longitudinal mixed model design was used to assess changes in future thinking in the different groups over time. METHODS: Parasuicide patients with a history of previous suicidal behaviour and personality disturbance were compared with a matched group of community controls on an adapted fluency measure of future thinking, which measured both quantitative and qualitative aspects of anticipated experiences. Patients were then randomly allocated to either the specific intervention (MACT) or treatment as usual (TAU) and assessed again at 6 month follow-up. RESULTS: Parasuicide patients showed reduced positive future thinking but no increased negative future thinking. Patients who received MACT showed a significant improvement in positive future thinking over the follow-up period whereas the TAU group showed no such improvement. However, interpretation of this finding was made more difficult by the control group also showing a significant improvement in positive future thinking. CONCLUSION: The results confirm that parasuicide patients exhibit a relative deficit in positive future thinking and suggest that this lack of positive future thinking may be remedied, at least partly, by a brief intervention.

Adolescent↗

PubMed1997

Potential for hostility and faking-good in high-hostile men.

We investigated if Type A Structured Interview (SI)-assessed hostility (PoHo) is subject to voluntary underreporting, or faking-good, by hostile subjects. Sixteen men who previously scored above the clinical cutoff of 3 on SI hostility were randomly assigned to an experimental (N = 8) or control (N = 8) group. Both groups underwent a second videotaped SI, prior to which experimental subjects were asked to present themselves in a favorable light. Repeated-measures ANOVA revealed that experimental subjects were able successfully to decrease their global PoHo scores when instructed to do so (38% scored below the clinical cutoff score). The SI-derived hostility score is vulnerable to faking-good, and attention should be paid to both the motivational set of subjects and the instructions given prior to the SI.

Adult↗

PubMed1997

Longitudinal neuropsychological outcome in infants and preschoolers with traumatic brain injury.

Neuropsychological outcome was evaluated in a prospective, longitudinal follow-up study of children age 4 months to 7 years at injury with either mild-to-moderate (N = 35) or severe (N = 44) traumatic brain injury (TBI). Age-appropriate tests were administered at baseline, 6 months, 12 months, and 24 months after the injury. Performance was compared on (1) Composite IQ and motor, (2) Receptive and expressive language, and (3) Verbal and Perceptual-Performance IQ scores. In comparison to mild-to-moderate TBI, severe TBI in infants and preschoolers produced deficits in all areas. Interactions between task and severity of injury were obtained. Motor scores were lower than IQ scores, particularly after severe TBI. Both receptive and expressive scores were reduced following severe TBI. Expressive language scores were lower than receptive language scores for children sustaining mild-to-moderate TBI. While severe TBI lowered both Verbal and Perceptual-Performance IQ scores, Verbal IQ scores were significantly lower than Perceptual-Performance IQ scores after mild-to-moderate TBI. Mild injuries may produce subtle linguistic changes adversely impacting estimates of Verbal IQ and expressive language. Within the limited age range evaluated within this study, age at injury was unrelated to test scores: The impact of TBI was comparable in children ages 4 to 41 months versus 42 to 72 months at the time of injury. All neuropsychological scores improved significantly from baseline to the 6-month follow-up. However, no further change in scores was observed from 6 to 24 months after the injury. The persistent deficits and lack of catch-up over time suggest a reduction in the rate of acquisition of new skills after severe TBI. Methodological issues in longitudinal studies of young children were discussed.

Age Factors↗

PubMed1996

A modular xylanase from mesophilic Cellulomonas fimi contains the same cellulose-binding and thermostabilizing domains as xylanases from thermophilic bacteria.

The xynC gene from mesophilic Cellulomonas fimi encodes a large 125 kDa modular xylanase (XYLC), consisting of six distinct functional domains. In addition to a single Family 10 catalytic domain, XYLC contains a domain homologous with the nodulation protein, NodB, from nitrogen-fixing bacteria and thermostabilizing and cellulose-binding domains found previously only in xylanases from thermophilic bacteria.

Actinomycetales↗

PubMed1996

Gender differences in the relation between interview-derived hostility scores and resting blood pressure.

We examined the correlations between Structured Interview (SI)-derived hostility scores and resting blood pressure (BP) to see if they would be the same or different for healthy men and women. Standard risk factor information and resting BP measures were obtained from 193 undergraduates (109 men, 84 women), who underwent the SI. Subjects were rated for Potential for Hostility, Hostile Style, Intensity and Content, and completed Antagonism and Neuroticism scales. As expected, SI hostility scores were related to higher resting SBP in men, however; in women, they were related to lower resting SBP and Neuroticism. Regression analyses controlling for standard CHD risk factors indicated that SI-derived hostility predicted resting SBP and hypertensive status in both men and women, though in opposite directions. Thus, SI-derived hostility may assess a different construct in women than in men.

Arousal↗