Search PubMed⌕ Search

Biomedical subjects

D Kerrigan

Publications and source records attributed to D Kerrigan.

At least 19 recordsLinked to original sources
PubMed1996

Local anaesthesia for major general surgical procedures. A review of 116 cases over 12 years.

Between 1980 and 1992, 116 patients had either a simple mastectomy (32) or intra-abdominal procedures (84) under local anaesthesia (0.5-1% lignocaine with 1:200 000 adrenaline). A wide variety of general surgical procedures were feasible using only supplementary intravenous sedation (54%). Complications were uncommon and related to surgical procedure (three incorrect diagnoses, three procedures impossible) rather than the anaesthetic technique. There were no anaesthetic toxicity or postoperative problems. Local anaesthesia is extremely safe and facilitates larger surgical procedures than is generally appreciated.

Abdomen↗
PubMed1993

Bot-fly bite.

Explore the source record for details and available documents.

Adult↗
PubMed1992

Overexpression of P-glycoprotein and alterations in topoisomerase II in P388 mouse leukemia cells selected in vivo for resistance to mitoxantrone.

The overexpression of P-glycoprotein (PGP) and alterations in DNA topoisomerase II (TOPO II) were evaluated in mouse leukemia P388 cells selected in vivo for mitoxantrone (MTT) resistance (P388/MTT) and compared to doxorubicin (DOX) resistant (P388/DOX) or vincristine (VCR) resistant (P388/VCR) models. Among a panel of TOPO II inhibitors which included etoposide (VP-16), DOX, MTT and 4'-[(9-acridinyl)-amino]methanesulfon-m-anisidide (m-AMSA), the relative resistance compared to parental sensitive P388/S cells was: P388/DOX greater than P388/MTT greater than P388/VCR. All the resistant sublines exhibited minimal cell kill (less than 20%) at vincristine concentrations greater than 100-fold the IC50 for P388/S cells. In a soft-agar colony-forming assay, the modulation of cytotoxicity in P388/MTT cells by the calmodulin inhibitor trifluoperazine following a 3-hr drug treatment demonstrated a marked potentiation in cell kill with MTT, VP-16, DOX and m-AMSA but not VCR. Immunoblotting data revealed that while PGP was not detectable in P388/S cells, the overexpression of PGP was apparent in P388/MTT cells and the relative expression between the resistant sublines was: P388/DOX greater than P388/MTT greater than P388/VCR. Although the amount and DNA cleavage activity of TOPO II in nuclear extracts from P388/VCR cells were comparable to those in P388/S cells, they were markedly lower in both P388/DOX and P388/MTT cells. However, decatenation activity of TOPO II in nuclear extracts was comparable between the sensitive (P388/S) and resistant sublines (P388/MTT, P388/DOX, and P388/VCR). Results from the present study demonstrated that P388 cells selected for resistance to mitoxantrone exhibit changes in TOPO II and overexpression of PGP similar to P388/DOX cells, while vincristine resistant cells only overexpress PGP. Since therapeutic strategies are primarily designed to interfere with PGP-mediated drug efflux, the choice of agents for modulating resistance in tumors which overexpress PGP versus tumors which overexpress PGP with altered TOPO II could be different.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1992

Sequential administration of camptothecin and etoposide circumvents the antagonistic cytotoxicity of simultaneous drug administration in slowly growing human colon carcinoma HT-29 cells.

We compared the cytotoxicity of simultaneous and sequential combination chemotherapy with camptothecin and etoposide, in slowly growing human colon carcinoma, HT-29 cells. Simultaneous treatments of HT-29 cells with etoposide and camptothecin produced no marked enhancement of cytotoxicity over single agent administration. This finding demonstrates antagonism of one drug's cytotoxicity over the other. When these studies were repeated in sequential treatment protocols, we observed that antagonism could be circumvented if the period between individual drug administration was separated by 6-8 h. The cytotoxicity that was observed with this approach was never more than additive and the order of camptothecin or etoposide administration did not significantly affect the extent of combined cytotoxicity observed. The protective effect of simultaneous camptothecin and etoposide exposure was not due to reduced formation or alterations in the rate of cleavable complex reversal, and protection persisted for a considerably longer period of time than DNA strand breaks. Protection correlated with the kinetics of DNA and RNA synthesis inhibition produced by either drug. Remarkably, full cytotoxic protection could be afforded by one drug over the other, in the presence of only partial inhibition of DNA or RNA synthesis (50-60%). Our findings suggest that sequential rather than simultaneous administration of topoisomerase I and II inhibitors in future cancer chemotherapy schedules will enhance cytotoxicity over single-agent administration.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1991

Differential induction of secondary DNA fragmentation by topoisomerase II inhibitors in human tumor cell lines with amplified c-myc expression.

In order to understand the cellular events associated with cell death after the formation of topoisomerase II-DNA cleavable complexes, we compared the induction of endonucleolytic DNA fragmentation by etoposide and its more potent analog, teniposide (VM-26) in the human cell lines HT-29 and HL-60. A new filter-binding assay is described, which allows rapid quantification of nonprotein-linked DNA fragmentation involved in apoptosis. Both cell lines showed similar loss of colony formation ability following 30 min of treatment with various VM-26 concentrations even though the initial topoisomerase II-mediated DNA single-strand break frequency was higher in HL-60 cells. DNA repair studies following drug removal indicated that VM-26-induced DNA breaks reversed rapidly and completely in HT-29 cells, while in HL-60 cells, the initial lesions persisted at and above 5 microM VM-26. In both cell lines, topoisomerase II cleavage complexes, as measured by DNA-protein cross-links by alkaline elution, reversed rapidly and completely within 2-3 h. Secondary DNA fragmentation resembling chromatin endonucleolytic cleavage by apoptosis could be detected in HL-60 cells 3 h after VM-26 or etoposide treatment but not in HT-29 cells. Secondary DNA fragmentation was also induced in the human colon cancer cell lines COLO 320, which have c-myc amplification. Since HL-60 cells also have c-myc amplification and HT-29 do not, it is possible that c-myc overexpression may be involved in secondary DNA fragmentation. Finally, our results indicate heterogeneity of cell death mechanisms after exposure to topoisomerase II inhibitors among human cancer cell lines.

Adenocarcinoma↗
PubMed1991

Effect of local DNA sequence on topoisomerase I cleavage in the presence or absence of camptothecin.

In order to investigate the mechanism of topoisomerase I inhibition by camptothecin, we studied the induction of DNA cleavage by purified mammalian DNA topoisomerase I in a series of oligonucleotides and analyzed the DNA sequence locations of preferred cleavage sites in the SV40 genome. The oligonucleotides were derived from the sequence of the major camptothecin-induced cleavage site in SV40 DNA (Jaxel, C., Kohn, K. W., and Pommier, Y. (1988) Nucleic Acids Res. 16, 11157 to 11170) with the cleaved bond in their center. DNA length was critical since cleavage was detectable only in 30 and 20 base pair-(bp) oligonucleotides, but not in a 12-bp oligonucleotide. Cleavage was at the same position in the oligonucleotides as in SV40 DNA. Its intensity was greater in the 30- than in the 20-bp oligonucleotide, indicating that sequences more than 10 bp away from the cleavage site may influence intensity. Camptothecin-induced DNA cleavage required duplex DNA since none of the single-stranded oligonucleotides were cleaved. Analysis of base preferences around topoisomerase I cleavage sites in SV40 DNA indicated that camptothecin stabilized topoisomerase I preferentially at sites having a G immediately 3' to the cleaved bond. Experiments with 30-bp oligonucleotides showed that camptothecin produced most intense cleavage in a complementary duplex having a G immediately 3' to the cleavage site. Weaker cleavage was observed in a complementary duplex in which the 3'G was replaced with a T. The identity of the 3' base, however, did not affect topoisomerase I-induced DNA cleavage in the absence of drug. These results indicate that camptothecin traps preferentially a subset of the enzyme cleavage sites, those having a G immediately 3' to the cleaved bond. This strong preference suggests that camptothecin binds reversibly to the DNA at topoisomerase I cleavage sites, in analogy to a model previously proposed for inhibitors of topoisomerase II (Capranico, G., Kohn, K.W., and Pommier, Y. (1990) Nucleic Acids Res. 18, 6611-6619).

Animals↗
PubMed1991

Cell death induced by topoisomerase inhibitors. Role of calcium in mammalian cells.

Although the stabilization of topoisomerase II cleavable complexes by etoposide (VP-16) has been recognized to be important for cell killing, the lethal events following the formation of cleavable complexes remain to be elucidated. In an attempt to characterize the biochemical requirements for VP-16-induced cytotoxicity, we examined the effects of calcium depletion in Chinese hamster DC3F cells. Four-hour preincubation in calcium-free medium or in complete medium containing 5 mM [ethylenebis(oxyethylenenitrilo)]tetraacetic acid (EGTA) protected against the cytotoxicity of VP-16. Under these same conditions, the VP-16-induced DNA single-strand break frequency in calcium-depleted cells remained similar to that of control cells. Cell-cycle analysis and thymidine pulse incorporation indicated that calcium depletion did not alter DNA synthesis and cell cycle distribution. Drug-induced cytotoxicity was restored progressively within 4-8 hr after calcium-depleted cells were refed with calcium-containing medium. Calcium depletion also protected against the cytotoxicity of camptothecin, hyperthermia and, to a lesser extent, nitrogen mustard and gamma radiation in DC3F cells. Similar results were obtained in human colon carcinoma HT-29 cells. Our results suggest that topoisomerase II-mediated DNA breaks are only potentially lethal and that calcium-dependent cellular processes are required for the cytotoxicity of topoisomerase inhibitors.

Animals↗
PubMed1991

Relationship of DNA strand breakage produced by bromodeoxyuridine to topoisomerase II activity in Bloom-syndrome fibroblasts.

Cells from patients with Bloom syndrome, a cancer-prone disorder with cutaneous photosensitivity and spontaneous chromosome breakage, exhibit an abnormally increased number of sister-chromatid exchanges following treatment with 5-bromodeoxyuridine (BrdU). This effect has been postulated to be mediated by abnormal topoisomerase II activity. We used alkaline elution to measure DNA single-strand breakage following prolonged exposure to BrdU. Five-day exposure to BrdU produced equal numbers of alkali-labile sites in normal and Bloom-syndrome fibroblasts. These breaks were not protein-associated but were produced by alkali. Treatment with topoisomerase II inhibitors induced similar frequencies of DNA single-strand breaks in normal and Bloom-syndrome fibroblasts. These findings imply that BrdU incorporation into cellular DNA induces alkali-labile DNA lesions that are independent of topoisomerase II activity in Bloom and normal cells.

Bloom Syndrome↗
PubMed1991

S-phase population analysis does not correlate with the cytotoxicity of camptothecin and 10,11-methylenedioxycamptothecin in human colon carcinoma HT-29 cells.

Previous studies in rapidly proliferating rodent cells have suggested that the lethal effect of the DNA topoisomerase I inhibitor, camptothecin (CPT) is dependent upon the active participation of DNA replication (Holm et al. Cancer Res. 49:6365-6368; 1989). The purpose of the current study was to determine if this relationship applies to more slowly growing human cells. In our present study, we employed the human colon carcinoma cell line, HT-29 (45 hr doubling time). Flow cytometric determination of S-phase cells either by S-phase fit model or rectangle fit model analysis predicted that 21% of exponentially growing HT-29 cells were undergoing DNA replication. These findings were confirmed by immunofluorescence microscopy of bromodeoxyuridine labeled cells. Based on these findings, we would have expected only 20-30% of the cells to be susceptible to brief treatment (30 min) with CPT. Instead, 90-95% of HT-29 cells were killed. This apparent disparity was not due to prolonged cellular retention of drug after treatment because protein-linked DNA strand breaks reversed within 15 min of drug removal. Moreover, the DNA replication inhibitor, aphidicolin, fully protected HT-29 cells against CPT-induced killing but did not affect the production of CPT-induced protein-linked DNA strand breaks. Similar results were also obtained using the CPT-analog, 10,11-methylenedioxy-camptothecin, which was 5- to 10-fold more potent than camptothecin (O'Connor et al. Cancer Commun. 2:395-400; 1990).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Trifluoperazine modulation of resistance to the topoisomerase II inhibitor etoposide in doxorubicin resistant L1210 murine leukemia cells.

Murine leukemia L1210 cells selected for progressive resistance to doxorubicin (DOX) display both the multidrug resistant (MDR) phenotype and reductions in drug induced topoisomerase II-mediated DNA cleavage in nuclear extracts (Ganapathi, R.; Grabowski, D.; Ford, J.; Heiss, C.; Kerrigan, D.; Pommier, Y., Cancer Commun. 1:217-224; 1989). The present study was performed to characterize the results of exposure of the sensitive (S) and progressively DOX-resistant (10-fold, R1, and 40-fold, R2) L1210 cells to the topoisomerase II inhibitor, etoposide, and to investigate the modulating effects of the calmodulin inhibitor, trifluoperazine (TFP). Immunoblotting experiments indicated no apparent decrease in the p170 or p180 isoforms of topoisomerase II in the resistant sublines versus parental sensitive cells. Cross-resistance to etoposide (VP-16) was similar to that of DOX (10- and 40-fold). A non-cytotoxic concentration of 5 microM TFP enhanced cell kill 1.5- fold in the sensitive and 3- to 5-fold in the progressively DOX-resistant cells. Accumulation of VP-16 was 30% to 50% lower in the resistant sublines versus similarly treated sensitive cells, and a marked enhancement of drug uptake in the presence of TFP was observed in the sensitive but not in the resistant cells exposed to equivalent extracellular levels of VP-16. Although equimolar concentrations of VP-16 produced fewer DNA single strand breaks (SSB) and DNA protein crosslinks (DPC) in the resistant versus sensitive cells, similar DNA damage was apparent when S and R1, but not R2, cells were treated at VP-16 concentrations that produced equivalent cell death.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Phosphorylation of mammalian DNA topoisomerase I and activation by protein kinase C.

The influence of mammalian DNA topoisomerase I phosphorylation on enzyme activity has been investigated. Dephosphorylation by calf intestine alkaline phosphatase abolished the DNA relaxing activity of DNA topoisomerase I and the sensitivity of the enzyme to its specific inhibitor, camptothecin. DNA topoisomerase I could be reactivated by incubation with purified protein kinase C. DNA topoisomerase I was then able to relax supercoiled DNA processively, like the native enzyme, and to cleave 32P-end-labeled SV40 DNA fragments at the same sequences as the native enzyme in the presence of camptothecin. These results show that active DNA topoisomerase I is a phosphoprotein and suggest a possible regulatory role of protein kinase on topoisomerase I activity and on its sensitivity to camptothecin.

Alkaline Phosphatase↗
PubMed1990

Structure-activity relations, cytotoxicity and topoisomerase II dependent cleavage induced by pendulum ring analogues of etoposide.

The cytotoxicity of etoposide and its analogues, dihydroxy (DHVP), o-quinone (VP-Q) and o-methyl (VP-OMe), was evaluated in human breast (MCF-7) and HL60 tumour cells. Although less potent than etoposide, both DHVP and VP-Q were cytotoxic to these cells. However, VP-OMe was inactive. Studies with purified topoisomerase II showed that the intensity of DNA cleavage and the pattern of cleavage were similar for DHVP, VP-Q and etoposide. In contrast, the VP-OMe failed to induce DNA cleavage, indicating that the presence of 4'-OH is essential for metabolism, induction of topoisomerase II-mediated DNA cleavage and cytotoxicity of etoposide and its analogues.

Breast Neoplasms↗
PubMed1990

Reflex co-ordination of corporal and antral contractions in the conscious dog.

This study characterizes the role of extrinsic nerves in the co-ordination of corporal and antral contractions in the dog. Fasting motor activity was recorded in conscious dogs with stomachs previously divided into separate corporal and antral pouches. Both corpus and antrum showed synchronized phases of activity and quiescence recognizable as migrating motor complexes (MMCs, duration 81.2 +/- 9.6 min, n = 4). Moreover, individual contractions were temporally linked such that corpus contractions, occurring at 76 +/- 4 s intervals, were each followed by a burst of one to three antral contractions at a frequency of 4-5 min-1. The mean latency between the onset of individual contractions in the corpus and antrum was 10.9 +/- 2.6 s (n = 4). Denervation of the antral pouch in two additional dogs did not affect the MMC cycle (mean durations 106.6 and 82.1 min) and the onset of activity in the corpus and antrum was generally co-ordinated but less precise. However, individual antral contractions were no longer linked to corporal contractions, occurring randomly throughout the corpus contraction cycle. This was associated with a lower contraction frequency in the denervated antral pouches than in the corpus (0.3 +/- 0.1 min-1 compared to 0.6 +/- 0.08 min-1). It is proposed that a vagal reflex, excited by corporal tension receptors, provides phasic excitation facilitating the generation of antral contractions. Such a reflex is likely to reinforce the myogenic mechanisms which occur in the intact stomach and thus plays a role in co-ordinating gastric peristalsis.

Animals↗
PubMed1990

10,11-Methylenedioxycamptothecin, a topoisomerase I inhibitor of increased potency: DNA damage and correlation to cytotoxicity in human colon carcinoma (HT-29) cells.

We had previously shown that 10,11-methylenedioxy-20-(RS)-camptothecin (MDO-CPT) is a more potent inhibitor of purified DNA topoisomerase I than 20-(S)-camptothecin (CPT). The current studies compared the cytotoxicity and DNA damage induced by MDO-CPT and CPT in the human colon carcinoma cell line, HT-29. MDO-CPT was 7- to 10-fold more potent than CPT both for cytotoxicity (ID50 = 25 vs. 180 nM) and production of DNA single-strand breaks (SSB). Kinetics of SSB formation and reversal were similar for MDO-CPT and CPT. DNA-protein crosslinks (DPC) were also produced by both drugs with a SSB/DPC ratio of 1/1. Moreover, no SSB were detected under non-deproteinizing conditions, indicating that both CPT and MDO-CPT produced protein-linked DNA single-strand breaks. A good correlation between cytotoxic potency and protein-linked DNA single-strand break production was observed for CPT and MDO-CPT, implying a causal relationship between drug-induced cytotoxicity and topoisomerase I inhibition. The sensitivity of human colon HT-29 cancer cells to camptothecins may be a selective phenomenon since these cells normally express natural resistance to current chemotherapeutic drugs, including topoisomerase II inhibitors.

Camptothecin↗
PubMed1990

Malignant carcinoid within a recurrent sacrococcygeal teratoma in childhood.

Sacrococcygeal teratomas are uncommon tumors of childhood carrying a good prognosis if histologically benign and completely excised, especially if the coccyx is also excised. Carcinoids are also rare in children and only rarely associated with teratomas. We report the findings in a girl who had a malignant carcinoid within a recurrent malignant sacrococcygeal teratoma following its incomplete excision in the neonatal period. We believe that this is the first such case occurring in childhood.

Carcinoid Tumor↗
PubMed1989

Differential requirement of DNA replication for the cytotoxicity of DNA topoisomerase I and II inhibitors in Chinese hamster DC3F cells.

The cytotoxicity of topoisomerase inhibitors is thought to result from the induction of enzyme-mediated DNA breaks. The fact that these breaks reverse rapidly in cells programmed to die, led us to investigate further the cytotoxic mechanisms of topoisomerase I (camptothecin) and topoisomerase II inhibitors (VP-16 and amsacrine) in Chinese Hamster lung fibroblasts (DC3F). Exposures (30 min) to camptothecin produced limited cell killing with approximately 20% of the cells naturally resistant. This resistance was overcome by increasing the drug exposure time. Inhibition of DNA synthesis by 5-min pretreatments with aphidicolin or hydroxyurea abolished the cytotoxicity of camptothecin without changing the level of camptothecin-induced DNA breaks. A good correlation was found between the degree of DNA synthesis inhibition by aphidicolin and the reduction of camptothecin cytotoxicity. In similar experiments performed with topoisomerase II inhibitors, aphidicolin prevented only partially against VP-16- and amsacrine-induced cytotoxicities, yet had no effect upon drug-induced DNA breaks. These results indicate that the production of topoisomerase-mediated DNA breaks by antitumor drugs is not sufficient for cell killing. Instead, an interference of moving DNA replication forks with drug-stabilized topoisomerase-DNA complexes is critical for cell death. The cytotoxicity of camptothecin seemed to be completely related to this process, while that of topoisomerase II inhibitors seemed to involve additional mechanisms in DC3F cells.

Amsacrine↗