PubMed Health⌕ Search

Biomedical subjects

F Abbott

Publications and source records attributed to F Abbott.

At least 19 recordsLinked to original sources
PubMed2001

CYP2E1-mediated modulation of valproic acid-induced hepatocytotoxicity.

OBJECTIVES: To determine the cytotoxicity of valproic acid (VPA) and its metabolite, 4-ene-valproic acid (4-ene-VPA) in human hepatoblastoma cells (Hep G2), and to study the modulatory effect of cytochrome P450 2E1 induction in this model. METHODS: Cells were exposed to VPA or 4-ene-VPA in the presence of either ethanol (EtOH), or EtOH combined with disulphiram (DS). Some cells were exposed to alpha-fluoro-VPA or to alpha-fluoro-4-ene-VPA in the absence of CYP2E1 inducers. Apoptosis and necrosis were measured by analyzing 6000 cells per sample using transmission electron microscopy, while cytokine release and apoptosis were quantitated by ELISA. RESULTS: VPA + EtOH increased VPA cytotoxicity. 4-ene-VPA + EtOH significantly increased toxicity, while DS + EtOH significantly reduced this toxicity. Alpha-fluorinated analogues reduced cytotoxicity compared to the corresponding VPA compounds. Neither VPA nor alpha-fluorinated VPA increased the release of IL-6 or TNF-alpha in media. A significant increase in the release of TNF-alpha was observed in cells exposed to 4-ene-VPA that further increased with EtOH exposure. CONCLUSIONS: Cells exposed to 4-ene-VPA experience greater cytotoxicity than those treated with VPA. Cytochrome P450 2E1 inducers enhance toxicity in VPA-exposed cells, while alpha-fluorination of VPA diminishes cytotoxicity by directly interfering with the beta-oxidation of the 4-ene-VPA metabolite.

Anticonvulsants↗
PubMed1996

Attenuation of morphine-induced delirium in palliative care by substitution with infusion of oxycodone.

We have observed among patients of the Southern Community Hospice Programme that up to 25% experience acute delirium when treated with morphine and improve when the opioid is changed to oxycodone or fentanyl. This study aimed to confirm by a prospective trial that oxycodone produces less delirium than morphine in such patients. Oxycodone was administered by a continuous subcutaneous infusion, as this allowed more flexible and reliable dosing, and patients were monitored for any adverse reactions to the drug. Thirteen patients completed the study. Statistically significant improvements in mental state and nausea and vomiting occurred following a change from morphine to oxycodone. Pain scores improved but did not reach a level of statistical significance. The phenotype status of the patients was tested to establish their capacity to metabolize oxycodone. One patient who did not achieve adequate pain control proved to be a poor metabolizer. These results show that oxycodone administered by the subcutaneous route can provide effective analgesia without significant side effects in patients with morphine-induced delirium. This treatment allows patients to remain more comfortable and lucid in their final days. A small proportion of patients who do not metabolize oxycodone effectively may not receive this benefit.

Aged↗
PubMed1995

Plasma concentrations of fentanyl with subcutaneous infusion in palliative care patients.

1. Plasma concentrations of fentanyl were measured by g.c. in 20 patients (median age: 75 years and range: 54-86 years; eight females) in palliative care receiving the drug by continuous s.c. infusion (median rate: 1200 micrograms day-1 and range: 100-5000 micrograms day-1). 2. The infusion rate was significantly related to the duration of therapy (Spearman rho = 0.56, P < 0.05). The total steady-state plasma concentrations of fentanyl ranged between 0.1 and 9 ng ml-1, with a median of 1 ng ml-1. The unbound fraction of fentanyl in the plasma ranged from 17.8 to 44.4%, with a median value of 33.6%. Infusion rates and both total and unbound plasma concentrations of fentanyl were correlated (Spearman rho = 0.92, P < 0.05 in each case). Even with standardization for dosage, there was an eightfold variation in total plasma concentrations and 3.5-fold variation in unbound plasma concentrations of fentanyl. 3. There is considerable inter-patient variability in the pharmacokinetics of fentanyl with s.c. infusion in the palliative care setting, which necessitates careful titration of dosage according to individual clinical response.

Aged↗
PubMed1993

Treatment of chronic severe alopecia areata with topical diphenylcyclopropenone and 5% minoxidil: a clinical and immunopathologic evaluation.

BACKGROUND: Topical diphenylcyclopropenone (DPCP) and minoxidil have been used in the treatment of alopecia areata with variable results. OBJECTIVE: This study was designed to evaluate the efficacy of DPCP alone or in combination with topical 5% minoxidil for the treatment of chronic severe alopecia areata. The effect of therapy on cutaneous T-cell and Langerhans cell subpopulations and intercellular adhesion molecule-1 (ICAM-1) expression was also examined. METHODS: Fifteen patients with chronic (more than 2 years), severe (more than 50% scalp involvement) alopecia areata participated in a 24-week trial. Half of the scalp was treated with DPCP once weekly and with either 5% minoxidil solution or a vehicle solution twice daily in a randomized double-blind design. Skin biopsy specimens from each half of the scalp were obtained before therapy and after 12 and 24 weeks of therapy for histologic and immunophenotypic analysis. RESULTS: Thirteen patients completed the study. Five of 13 patients (38%) showed marked regrowth of coarse terminal hair after 24 weeks of treatment with DPCP. The addition of topical 5% minoxidil did not produce any significant clinical benefit in this 24-week trial. Immunophenotypic analysis showed no differences between responders and nonresponders at baseline. During treatment, Leu-4, Leu-2, Leu-3, and keratinocyte ICAM-1 expression were significantly reduced in biopsy specimens of responders versus nonresponders. CONCLUSION: DPCP treatment showed a 38% success rate in producing cosmetically acceptable regrowth in patients with chronic severe alopecia areata.

Administration, Cutaneous↗
PubMed1992

Glomerular mesangial cells and inflammatory macrophages ingest neutrophils undergoing apoptosis.

Apoptosis or programmed cell death of senescent neutrophils leading to their uptake by phagocytes is a general mechanism by which neutrophils may be removed from inflamed sites in vivo, promoting resolution rather than persistence of inflammation. We now report morphological evidence of neutrophil apoptosis leading to uptake by glomerular cells in rats with experimental glomerulonephritis. In addition to confirming that inflammatory macrophages take up apoptotic neutrophils, these studies indicated that glomerular mesangial cells can also participate in this mode of neutrophil clearance. Furthermore, human neutrophils which had been "aged" in vitro so as to undergo apoptosis were ingested by 31.5 +/- 1.3% (mean +/- SE) of cultured human mesangial cells, but there was minimal recognition of freshly isolated neutrophils (2.2 +/- 0.1%). Centrifugal elutriation of aged neutrophil populations yielded fractions with varying degrees of apoptosis (from 11.1 to 79.4%). Uptake of these fractions (by 8.2% to 59.8% of mesangial cells) was closely correlated with apoptosis (r = 0.96, P less than 0.0001). This demonstrated that recognition was dependent upon apoptosis, as in previous reports of macrophage recognition of aged neutrophils. However, by contrast, a partial requirement for serum was observed. These data indicate a hitherto unexpected function for the mesangial cell in clearance of senescent neutrophils from the glomerulus which may supplement inflammatory macrophage uptake of leucocytes undergoing apoptosis.

Animals↗
PubMed1992

Human mesangial cells synthesize interleukin 1 alpha but not interleukin 1 beta, interleukin 1 receptor antagonist, or tumour necrosis factor.

There is controversy over whether mesangial cells synthesize and release IL-1 and TNF, and many of the positive experiments were performed before specific reagents and molecular probes were available. Consequently we have stimulated human mesangial cells using protocols known to stimulate the synthesis of other cytokines. No mRNA for IL-1 beta or TNF could be detected in quiescent or proliferating mesangial cells irrespective of whether they had been exposed to cytokines or not. In contrast mRNA for IL-1 alpha was detected in cells stimulated with IL-1 beta 10 ng/ml or with TNF 500 ng/ml; IL-1 alpha was also detected in cell lysates from stimulated mesangial cells. We could not detect mRNA for IL-1 receptor antagonist in any of the cell preparations. These results suggest that mesangial cells are unlikely to be a major source of IL-1 beta or TNF.

Cells, Cultured↗
PubMed1991

Interleukin-1 beta stimulates human mesangial cells to synthesize and release interleukins-6 and -8.

Interleukin-1 beta (IL-1 beta) and tumor necrosis factor (TNF) have been reported to stimulate human mesangial cells (HMC) to proliferate and synthesize eicosanoids. We have examined whether they also induce HMC to release cytokines. In this study we show that both IL-1 and TNF stimulate HMC to release IL-6 and IL-8. Cycling and quiescent HMC were stimulated with various concentrations of either recombinant IL-1 beta or TNF for 1 to 24 hours. IL-1 beta at doses as low as 6 pg/ml stimulated mesangial cells to synthesize mRNA for both IL-6 and IL-8 as assessed by Northern analysis; mRNA for tubulin remained constant, which demonstrated a specific increase in mRNA. Secretion of IL-6 and IL-8 into the culture medium increased (4.5 to 18 ng/ml and 4 to 40 ng/ml, respectively) measured by ELISAs. TNF had similar effects but only in high concentrations (greater than 100 ng/ml). IL-1 beta did not stimulate cells to proliferate, as measured by 3H thymidine incorporation. TNF caused proliferation but only in concentrations over 100 ng/ml. We conclude that IL-1 beta is a potent stimulator of human mesangial cell production of IL-6 and IL-8, both of which may influence injury in nephritis. TNF also stimulates mesangial cells but only in pharmacological doses.

Cells, Cultured↗
PubMed1990

Metabolic profiling of valproic acid in patients using negative-ion chemical ionization gas chromatography-mass spectrometry.

A negative-ion chemical ionization gas chromatographic-mass spectrometric method for the determination of valproic acid (VPA) and fourteen of its metabolites in a single chromatographic run is reported. The assay features the use of four internal standards and is applicable to the analysis of small serum and urine volumes. A combination of pentafluorobenzyl and trimethylsilyl derivatization resulted in the [M - 181]- ion as the base peak for all the metabolites measured. When these ions were monitored sensitivities in the low picogram levels were achieved. The VPA metabolite profile was determined in pediatric patients on VPA monotherapy and on combined VPA therapy with either carbamazepine or clobazam. The recently characterized diene metabolite, (E,E)-2,3'-diene-VPA, was found to be a major serum metabolite of VPA. In the patient groups taking VPA in combination with carbamazepine, the induction of omega and omega-1 pathways of VPA metabolism was apparent, while the levels of the beta-oxidation products were significantly decreased.

Adolescent↗
PubMed1989

Autoantibodies to glomerular antigens in patients with Wegener's granulomatosis.

Patients with Wegener's granulomatosis have autoantibodies to a neutrophil cytoplasmic antigen. As these patients often present with severe glomerulonephritis we investigated whether the same autoantigen was expressed in glomeruli by using both cultured human glomerular cells and frozen normal human kidney sections. Glomeruli were isolated from normal human kidney cortex by differential sieving and plated on to coverslips in growth medium containing various supplements. Cell types were identified by a series of markers and designated either epithelial, endothelial or mesangial. In single and double staining experiments, glomerular cells were incubated with a monoclonal antibody to the neutrophil cytoplasmic antigen (MCAW8), control mouse monoclonal IgG, sera from patients with Wegener's granulomatosis and control normal human serum. MCAW8 and Wegener's patient sera bound specifically to cultured epithelial and endothelial cells. MCAW8 was also found to bind to the glomerular epithelium in frozen sections. We conclude that autoantibodies to glomerular antigens are present in serum of patients with Wegener's granulomatosis and may be important in the pathogenesis of rapidly progressive glomerulonephritis.

Antibodies, Monoclonal↗
PubMed1984

Monoamine oxidase inhibitors in South American hallucinogenic plants: tryptamine and beta-carboline constituents of ayahuasca.

Ayahuasca is a hallucinogenic beverage derived by boiling the bark of the Malpighiaceous liana Banisteriopsis caapi together with the leaves of various admixture plants, viz. Psychotria viridis, Psychotria carthagenensis , or Diplopterys cabrerana . B. caapi contains harmine, harmaline, and tetrahydroharmine while the admixtures contain N,N-dimethyltryptamine (DMT). DMT, a potent hallucinogen, is inactive orally due to degradation by visceral monoamine oxidase (MAO). The beta-carbolines, however, are highly active reversible inhibitors of MAO and may protect the DMT from deamination by MAO and render it orally active. This mechanism has been proposed to underlie the oral activity of ayahuasca but has not been experimentally confirmed. In the present study the constituents of the admixture plants and the alkaloids of eight ayahuasca samples from Peru were qualitatively and quantitatively analyzed using two-dimensional thin-layer chromatography (TLC), high pressure liquid chromatography (HPLC) and gas chromatography/mass spectrometry (GC/MS). Several B. caapi cultivars were quantitatively compared for variations in alkaloid content. Three admixture plants used rarely in the manufacture of ayahuasca were also screened for alkaloids. A selected sample of beta-carbolines were screened for activity as MAO inhibitors using an in vitro assay system, and structure/activity relationships were compared. Inhibition observed with single compounds was compared with the activity of selected samples of ayahuasca which were screened in the system and also with the activity of mixtures of beta-carbolines. The levels of DMT and beta-carbolines found in the ayahuasca samples examined in the present study were an order of magnitude greater than the levels reported in a previous study. Ayahuasca was found to be an extremely effective inhibitor of MAO in vitro and the degree of inhibition was directly correlated with the concentration of MAO-inhibiting beta-carbolines. Inhibition experiments using mixtures of beta-carbolines indicated that their effects in combination are additive, rather than synergistic or antagonistic. Implications of the results in understanding the pharmacology of ayahuasca are discussed.

Alkaloids↗
PubMed1983

Identification of valproic acid metabolites in human serum and urine using hexadeuterated valproic acid and gas chromatographic mass spectrometric analysis.

Valproic acid, an antiepileptic drug, is extensively metabolized in humans. A hexadeuterated valproic acid was used in this study to aid the identification of metabolites and their artifacts in serum and urine extracts. A 600 mg oral dose of hexadeuterated valproic acid was administered to a human volunteer at steady state serum concentrations of unlabelled valproic acid. By using gas chromatography mass spectrometry, metabolites were characterized as their methyl, tert-butyldimethylsilyl, or trimethylsilyl derivatives. A di-unsaturated metabolite with concentrations comparable to 2-ene valproic acid was identified in serum and urine. The presence of a molecular ion doublet in the mass spectrum corresponding to the unlabelled and hexadeuterated dienes reduces the possible structures for this metabolite. A new metabolite, 2-propyl-4-ketopentanoic acid was also identified in serum and in urine. The dicarboxylic acids, 2-propylsuccinic and 2-propylmalonic were identified in the urine extract as metabolites. Identification of isolated metabolites was aided by comparison of the retention times and mass spectra to those of synthesized reference compounds. Diagnostic fragment ions and ion doublets in the mass spectra of the derivatives of newly identified metabolites were compared to those of known metabolites.

Biotransformation↗
PubMed1976

Fluorescence energy-transfer measurements between the calcium binding site and the specificity pocket of bovine trypsin using lanthanide probes.

Using fluorescence energy-transfer experiments we have measured the distance between the specificity pocket and the calcium ion binding site of bovine pancreatic trypsin. Proflavin and thionine were used to block the specificity site, whereas various lanthanide ions were substituted for the calcium. It was then possible to choose various donor-acceptor pairs which exhibit suitable energy transfer. We have calculated the distance between proflavin and Nd(III), Pr(III), and Ho(III) to be 10.9, and 10.3, and 10.3 A, respectively. This agrees very well with the value of approximately 10 A we obtained between the methyl protons of p-toluamidine (a competitive inhibitor) and Gd(III) using nuclear magnetic resonance techniques (Abbott, F., Gomez, J.E., Birnbaum, E.R., and Darnall, D.W. (1975), Biochemistry 14, 4935). This is strong evidence that, in solution, the calcium binding site is composed of the side chains of Ser-190 and Asp-194.

Amino Acid Sequence↗
PubMed1975

The location of the calcium ion binding site in bovine alpha-trypsin and beta-trypsin using lanthanide ion probes.

The effect of Gd3+ on the nuclear magnetic resonance (NMR) relaxation rates, T1m-1 and T2m-1, of inhibitor protons in metal-inhibitor-trypsin ternary complexes has been measured. The Solomon-Bloembergen equations have been used to calculate distances of 10.0 +/- 0.5, 8.8 +/- 0.5, and 9.5 +/- 0.5 A between the metal ion and the methyl and ortho protons of p-toluamidine, and the methyl protons of acetamidine, respectively. Essentially the same results are obtained for both alpha-trypsin and beta-trypsin. Binding constants of 3.3 x 10(3) and 4.1 x 10(3) M-1 for the association of Gd(III) with alpha-trypsin and beta-trypsin, respectively, in the presence of p-toluamidine at pH 6.0 have been obtained by equilibrium dialysis. Calcium binding constants of 260 and 3700 M-1 at pH 6.0 and 8.0, respectively, with beta-trypsin have also been obtained. Calcium ion and gadolinium ion compete for the same site on the protein. Calcium has been shown to protect alpha-trypsin from further autolytic degradation to psi-trypsin. From examination of the crystal structure of the enzyme we propose that the calcium ion binding site of bovine trypsin is comprised of the side chains of Asp-194 and Ser-190 (based on the chymotrypsin sequence numbering system). This seems to be the only site which is comprised of at least one carboxyl group; which fits our distance requirements and which is conisistent with other chemical data.

Animals↗
PubMedDate not supplied

Setting up a shared care glaucoma clinic.

This article describes how a nurse-led clinic to care for patients with glaucoma was set up and provides some initial evidence of its success. The authors also explain how they have developed the clinic further and their plans for the future.

Glaucoma, Open-Angle↗
PubMedDate not supplied

Identification and characterization of the glutathione and N-acetylcysteine conjugates of (E)-2-propyl-2,4-pentadienoic acid, a toxic metabolite of valproic acid, in rats and humans.

The severe hepatotoxicity of valproic acid (VPA) is believed to be mediated through reactive metabolites. The formation of glutathione (GSH) and N-acetylcysteine (NAC) adducts of reactive intermediates derived from VPA and two of its metabolites, 2-propyl-4-pentenoic acid (4-ene-) and 2-propyl-2,4-pentadienoic acid [(E)-2,4-diene VPA], was investigated in the rat. Rats were dosed ip with 100 mg/kg of VPA, 4-ene-, or 2,4-diene-VPA, and methylated bile and urine extracts were analyzed by LC/MS/MS and GC/MS, respectively. The GSH conjugate of (E)-2,4-diene VPA was detected in the bile of rats treated with 4-ene- and (E)-2,4-diene VPA. The NAC conjugate was a major urinary metabolite of rats given (E)-2,4-diene VPA and was a prominent urinary metabolite of those animals given 4-ene VPA. The NAC conjugate was also found to be a metabolite of VPA in patients. Both the GSH and NAC adducts were chemically synthesized and their structures established to be 5-(glutathion-S-yl)3-ene VPA and 5-(N-acetylcystein-S-yl)3-ene VPA by NMR and mass spectrometry. In contrast to the very slow reaction of the free acid of (E)-2,4-diene VPA with GSH, the methyl ester reacted rapidly with GSH to yield the adduct. In vivo it appears the diene forms an intermediate with enhanced electrophilic reactivity to GSH as indicated by the facile reaction of the diene with GSH in vivo [about 40% of the (E)-2,4-diene VPA administered to rats was excreted as the NAC conjugate in 24 hr]. The characterization of the GSH and NAC (in humans and rats) conjugates of (E)-2,4-diene VPA suggests that VPA is metabolized to a chemically reactive intermediate that may contribute to the hepatotoxicity of the drug.

Acetylcysteine↗