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Biomedical subjects

M Buckley

Publications and source records attributed to M Buckley.

At least 55 records · Page 3Linked to original sources
PubMed1998

Pharmacodynamics of topoisomerase I inhibition: Western blot determination of topoisomerase I and cleavable complex in patients with upper gastrointestinal malignancies treated with topotecan.

Analogues of camptothecins are specific inhibitors of eukaryotic DNA topoisomerase I (topo I) that lead to DNA damage and, eventually, cellular cytotoxicity. Camptothecin analogues bind to this target enzyme in the course of its normal function and stabilize the DNA-enzyme adduct to form a "cleavable complex." Preclinical experiments using Western blot analyses have shown cleavable complex formation to be the key intermediate step in topo I inhibition. In this series of experiments, it was our goal to convert this laboratory technique into a useful clinical assay, allowing measurement of the target enzyme and detection of the key intermediate in clinical specimens taken from patients being treated with the topo I inhibitor topotecan. Because available antibodies were not sufficiently sensitive at the start of this project, we identified a highly specific human SCL-70 antibody from a patient with scleroderma, which allowed quantitative determination of topo I copy number in HeLa and HT-29 cell lines. Additional refinements of the Western blot technique were accomplished to improve signal:noise ratio. In surgical tumor specimens, we found the median topo I level to be 30.1 x 10(5) copies/cell for gastric adenocarcinomas, compared to 18.4 x 10(5) copies/cell for normal gastric mucosae in the same samples. For lung adenocarcinoma, the median protein level was 21.5 x 10(5) copies/cell, compared with the normal tissue counterpart protein level of 12.7 x 10(5) copies/cell. The median tumor:normal ratios from paired samples of these tumor types were 1.51 and 1.84, respectively. As part of a Phase II study evaluating the efficacy of topotecan (1.5-2.0 mg/m2 daily for 5 days) in upper gastrointestinal malignancies, we obtained tumor and normal mucosa biopsies in 11 patients with gastric or esophageal cancer, 30 min after administration on day 4 or 5. Three patients with gastric adenocarcinoma had stable disease as their best response, with the remainder of patients progressing. Improvement in Western blotting methodology allowed the quantitation of topo I levels in these gastric and esophageal cancer biopsies, which could be augmented by brief heating to release complexed topo I. We were also able to directly visualize high molecular weight topo I-containing bands, which were shown to be cleavable complexes by heat reversal, with restoration of the topo I Mr 100,000 band. Using this heat reversal technique, we determined the presence of cleavable complex in a total of 7 of 11 patient biopsy samples (5 tumors and 2 normal mucosae). In patients treated with topotecan on this dose and schedule, we determined that a median of 73% of the total tumor topo I was involved in cleavable complex (range, 18.3-91%). The intensity of the Mr 100,000 topo I band in biopsy specimens of patients receiving topotecan represented "free" or noncomplexed topo I. The median copy number for the residual, noncomplexed topo I (n = 11) was 7.36 x 10(5) copies/cell, significantly less than the median of 30.1 x 10(5) copies/cell for random tumor specimens from patients with gastric adenocarcinomas (P < 0.001). Pharmacodynamic analysis demonstrated a negative correlation between the noncomplexed topo I copy number and topotecan area under the curve (Spearman rank test: r(s) = -0.81, P = 0.003). Nonlinear regression analyses of these data were best fit with an inhibitory maximum effect model, yielding parameter estimates for Emax and EC50 of 29.3 x 10(5) copies/cell (coefficient of variation = 22%) and 43.1 ng x h/ml (coefficient of variation = 27%), respectively. Through a series of careful modifications and refinements, we have improved the Western blot assay for topo I for use in clinical monitoring. We have demonstrated the ability to directly visualize cleavable complex in patients being treated with topo I inhibitor therapy and have directly quantitated free topo I, as well as the key topo I intermediate (cleavable complex), in biopsy specimens obtained from pat

Adenoma, Islet Cell↗
PubMed1997

The prevention of graft-versus-host disease by the serum of liver retransplanted rats.

The effect of serum from orthotopic liver retransplanted rats (re-OLT serum) on graft-versus-host disease (GVHD) was studied in rats. In the re-transplantation model of rat liver, orthotopic liver transplantation (OLT) was carried out in the DA (RT1a) into PVG (RT1c) combination; two days later the DA liver was removed and a new PVG liver implanted into the same recipient (re-OLT). In the in vivo GVHD model, male PVG rats were sublethally irradiated and injected intravenously with 3 x 10(8) DA or BN (RT1n) spleen through the penial vein. Within 1 h of the inoculation, rats of the experimental group were injected with 1 ml of re-OLT serum taken at postoperative day (POD) 7. Rats in the control group received 1 ml of normal PVG serum or syngeneic re-OLT serum (PVG-PVG, PVG-PVG). All PVG rats in the control groups died of GVHD within 21 days after the inoculation of DA or BN spleen lymphocytes. However, when the animals were treated with re-OLT serum, 100% (6/6) of the rats survived more than 60 days, following inoculation with DA lymphocytes but not with BN lymphocytes. The POD 7 re-OLT serum showed a strong inhibition against DA anti-PVG mixed lymphocyte reaction (MLR), although re-OLT serum did not contain soluble DA class I antigens, anti-DA class I or II antibody. The potential GVHD inhibitory factors in re-OLT serum may be two unique immunosuppressive proteins, which have been detected by SDS PAGE and reported previously. We conclude that re-OLT serum has immunosuppressive factors, which, at least in part, prevented the induction of GVHD in rats.

Animals↗
PubMed1997

Pancreatitis induced by codeine: a case report with positive rechallenge.

A woman who developed acute pancreatitis following ingestion of low dose codeine, with positive rechallenge, is described. As this is the first case report of pancreatitis being induced solely by codeine, this side effect must be rare in view of the widespread consumption of this drug.

Acute Disease↗
PubMed1996

Restoration of tolerance to rat hepatic allografts by spleen-derived passenger leukocytes.

The tolerance induced by orthotopic liver transplantation (OLT) in certain combinations of rat strains can be prevented by total body irradiation (TBI) of the donor. We demonstrate here that the intravenous inoculation of splenic leukocytes into irradiated donors before OLT could re-establish tolerance in association with a state of microchimerism detected in the recipients. When donor DA (RT1a) strain rats were irradiated with 1000 rad 24 h before liver harvesting and subsequent liver implantation into PVG recipients, five out of six rats died from rejection in this normally tolerogenic OLT (DA-PVG) combination. Injection of 1.5 x 10(8) splenic leukocytes from naive DA rats into the irradiated DA donor rats 24 h before OLT restored the tolerogenic potential of the liver allografts. Immunofluorescence assay revealed an increased number of donor (DA) type cells in the PVG recipient bearing a repopulated DA liver, compared to the PVG recipient of an irradiated liver. These results suggest that passenger leukocytes reconstituted by splenic leukocytes have the capacity to protect liver allografts.

Animals↗
PubMed1996

Methohexital infusion technique for conscious sedation.

PURPOSE: The purpose of this study was to evaluate a methohexital infusion technique for conscious sedation in oral surgical procedures. Patients were evaluated for recall, comfort, recovery, and surgeon's estimate of cooperation. MATERIALS AND METHODS: Twenty adult (mean age, 29 years) ASA I or II patients requiring various dentoalveolar procedures were entered into the study. Administration of 1.5 micrograms/kg fentanyl and 1 mg midazolam were given until sedation was achieved. An infusion of methohexital was started using 50 micrograms/kg/min and increased as needed to 75 micrograms/kg/min. Postoperatively, visual analog scales were used to evaluate the efficacy of the technique. RESULTS: The average total amount of methohexital infused was 257 mg for an average surgical time of 88 minutes. Recovery times were short and uneventful. Patients were cleared for discharge in under 35 minutes. No cardiac or respiratory side effects were noted other than a mild increase ( < 15%) in heart rate. Shivering and hiccoughing were noted in two and four cases, respectively. Recall of surgical events reported by patients was low and patient cooperation was high as reported by surgeons. CONCLUSION: The continuous infusion of methohexital for conscious sedation has been shown to be safe, effective, inexpensive, and well accepted by patients and surgeons.

Adolescent↗
PubMed1996

Relationship of the infraorbital nerve and vessels in the pathogenesis of idiopathic trigeminal neuralgia: a theoretical discussion and cadaveric study.

Many etiologies have been postulated to explain the pathogenesis of Trigeminal Neuralgia (TN). Most theories focus on a demyelinating process resulting in ephaptic transmission and recruitment of small pain fibers or a restrictive relationship of the superior cerebellar arteries and the trigeminal nerve roots at the level of the pons which may lead to demyelination. It is postulated that vasodilation or constriction of these vessels in a confined bony canal can create localized regions of demyelination and restrictive relationships creating painful stimuli. It is the purpose of this study to grossly investigate the relationship of the infraorbital nerve and vessels passing through the infraorbital canal to discuss whether their relationship may play a role in the pathogenesis of idiopathic TN. Patterns of relationship have been elucidated and will be described. This preliminary gross anatomical study should set the framework from which to base further microscopic and clinical studies.

Decompression, Surgical↗
PubMed1996

Clarithromycin resistance in Helicobacter pylori: prevalence in untreated dyspeptic patients and stability in vitro.

Susceptibilities to clarithromycin and metronidazole of 444 Helicobacter pylori isolates cultured from antral biopsies of 444 dyspeptic patients were determined by disc diffusion tests (15 mu g disc for clarithromycin, 5 mu g disc for metronidazole). Susceptibility of 46 of these isolates to erythromycin (5 mu g disc) was also tested. Minimal inhibitory concentrations (MICs) of clarithromycin for 42 selected isolates were determined by a plate dilution method. A zone diameter of 30 mm was defined as a 'cut-off' size differentiating susceptibility and resistance of the organism to clarithromycin, by comparing results obtained with the two methods. Of the 444 isolates, 424 (95.5%) were highly sensitive to clarithromycin, with zone diameters ranging from 30 to 98 mm. Twenty isolates (4.5%) were defined as resistant to clarithromycin, with zone diameters ranging between 6 and 28 mm. The incidence of clarithromycin resistance was similar in men and women and in different age groups, and was not significantly different between patients with peptic ulcer and non-ulcer dyspepsia. Among the 444 isolates, 168 (37.8%) were metronidazole resistant. There was cross resistance between clarithromycin and erythromycin, but not between clarithromycin and metronidazole. Stability of clarithromycin resistance was evaluated by the disc diffusion test and confirmed by the plate dilution method. Among the 20 clarithromycin-resistant isolates, nine (45%) reverted to be sensitive after 25 subcultures on drug-free agar. The findings in this study indicate that the incidence of clarithromycin-resistant H. pylori in untreated dyspeptic patients is low. Cross-resistance occurs between macrolides and resistance to clarithromycin in some strains is reversible.

Adult↗
PubMed1996

Helicobacter pylori and dyspepsia.

Non-ulcer dyspepsia (NUD) is a common condition that often goes unrecognized. Although approximately 50% of patients with NUD are infected with Helicobacter pylori, attempts to establish a link between this organism and the pathogenesis of NUD have yielded conflicting results. Recent studies have shown that eradication of H. pylori leads to improvements in symptoms in patients with NUD, and have highlighted the importance of long-term follow-up in this condition. It is possible that patients with NUD and H. pylori infection have a discrete condition that forms part of a spectrum of peptic ulcer disease. Hence, it may soon be possible to recommend H. pylori eradication treatment for patients with NUD.

Dyspepsia↗