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F M Williams

Publications and source records attributed to F M Williams.

At least 55 records · Page 3Linked to original sources
PubMed1996

Structural organization of the reduced folate carrier gene in Chinese hamster ovary cells.

The reduced folate carrier gene (rfc) encodes a putative protein that is involved in the intracellular accumulation of folates. In this report, we describe the organization of the rfc gene from Chinese hamster ovary cells. The hamster rfc gene contains 7 exons and 6 introns, which span 15.3 kilobases. It codes for two alternatively spliced messenger RNAs, one that contains all 7 exons and one that lacks exon 2 but contains the remaining 6 exons. The transcriptional start of the gene has been mapped to six sites approximately 200 base pairs upstream of the putative ATG initiation codon. The promoter region has no TATA box-like sequence but contains a consensus Sp1 binding site. This is the first report of the genomic structure of the reduced folate carrier gene from any species.

Alternative Splicing↗
PubMed1996

Neutrophils and myocardial reperfusion injury.

Ischaemia induces an acute inflammatory response in myocardial tissue with an early phase of neutrophil accumulation, which is accelerated by reperfusion. In experimental models, interventions that deplete neutrophils or inhibit their function cause a significant reduction in myocardial infarct size. These cells, therefore, may exacerbate tissue injury through the release of free radicals and proteolytic enzymes. Neutrophil recruitment depends on the presence of inflammatory mediators. Leukotriene B4, interleukin 8 and the complement fragment C5a have been implicated in this process. Studies using antibodies to the selectin, integrin and immunoglobulin superfamily adhesion molecules indicate that they also have a crucial role in myocardial neutrophil recruitment.

Animals↗
PubMed1996

Effects of nitrogen oxides on natural killer cells in glass craftsmen and braziers.

OBJECTIVES: To assess the effect of exposure to nitrogen oxides on peripheral blood natural killer cells. METHODS: Groups of glass craftsmen and braziers exposed to nitrogen oxides and non-exposed controls were studied. Air concentrations of nitrogen oxides were measured. Mononuclear cells isolated from peripheral blood samples were assayed for natural killer cell activity with K562 target cells in a 51Cr release assay and the percentage of natural killer cells (CD16) was measured by flow cytometry. RESULTS: Braziers were exposed to 1.2 ppm nitrogen dioxide and 8.6 ppm nitric oxide and glass craftsmen to 2.9 ppm nitrogen dioxide and 26.5 ppm nitric oxide. The natural killer cell activity of exposed workers was significantly lower than in non-exposed controls (P < 0.05 ANOVA Scheffe test). The percentage of natural killer cells in glass craftsmen was significantly greater than in controls (P < 0.05 ANOVA Scheffe test). Regression of natural killer cell activity against age, smoking habit, number of years worked and current exposure to nitrogen dioxide and nitric oxide gases was not significant. The percentage of natural killer cells was not significantly correlated with age, smoking habit, or numbers of years worked, but was significantly related to air concentrations of nitrogen dioxide (P < 0.01) and nitric oxide (P < 0.001). CONCLUSION: Natural killer cell activity and the percentage of natural killer cells in peripheral blood cells were altered in workers exposed to nitrogen oxides.

Adolescent↗
PubMed1996

The effect of sulphur mustard on glutathione levels in rat lung slices and the influence of treatment with arylthiols and cysteine esters.

1. Sulphur mustard reacts directly with benzenethiols and cysteine esters in aqueous medium. 2. Benzenethiols diffuse into lung slices in short term culture. 3. Treatment of lung slices in short term culture with benzenethiols does not protect cellular glutathione from conjugation with sulphur mustard. 4. Following uptake of cysteine ester into lung slices cysteine is elevated but this does not protect cellular glutathione from sulphur mustard.

Animals↗
PubMed1995

Isolation of a human cDNA that complements a mutant hamster cell defective in methotrexate uptake.

A clone has been isolated from a human lymphoblastic cDNA expression library that complements a mutant Chinese hamster cell defective in the uptake of the folate analogue methotrexate. When transfected with this clone the mutant cells regain the ability to transport the drug and, as a consequence, become sensitive to its cytotoxic action. The clone is 2863 base pairs long and has an open reading frame of 1770 base pairs that codes for a putative protein of 64 kDa. The putative protein has 51 and 50% identity at the amino acid level with the mouse and hamster functions, respectively, involved in the transport of reduced folates. Together these three proteins share 47% identity and have similar predicted structural features. The data are consistent with this human clone encoding either the reduced folate transporter or an auxiliary function that interacts with this transporter.

Amino Acid Sequence↗
PubMed1995

Prediction of the percutaneous penetration and metabolism of dodecyl decaethoxylate in rats using in vitro models.

Percutaneous absorption of a lipophilic surfactant, dodecyl decaethoxylate, can be predicted using in vitro models. In vivo, dermal penetration of dodecyl decaethoxylate was found to be 22.9% in 48 h. All of the absorbed dodecyl decaethoxylate in the rat was metabolised and excreted in expired air as carbon dioxide, or in the urine and faeces. Using rat skin mounted in the unoccluded flow-through diffusion cell with MEM as receptor fluid, in vivo absorption was predicted by the percentage of the applied dose recovered in the stratum corneum, epidermis, dermis and receptor fluid at 24 h (25%). Conversely, the penetration of dodecyl decaethoxylate was over-predicted in the unoccluded static diffusion cell using aqueous ethanol (50% v/v) as the receptor fluid where 49.4% recovered in the receptor fluid at 24 h. In vitro models may be used to predict percutaneous absorption and reduce animal use, provided a suitable receptor fluid is used in which the penetrant is soluble. Dermal metabolism of dodecyl decaethoxylate was low and not considered to influence dermal absorption.

Administration, Topical↗
PubMed1995

Ambient, biological, and biological effect monitoring of exposure to polycyclic aromatic hydrocarbons (PAHs).

A novel strategy was utilised to assess the risk to health from exposure to polycyclic aromatic hydrocarbons (PAHs). Ambient monitoring was carried out by personal sampling. Urinary thioethers (UTh) and urinary 1-hydroxypyrene (1-HP) were utilised for biological monitoring. Urinary d-glucaric acid (UDGA) and sister chromatid exchange (SCE) in peripheral blood lymphocytes were used as biological effect markers. The population was categorised into exposed and control groups according to the external dose of PAHs. The excretion of 1-HP in the controls over the 3-day period showed a relatively stable baseline, while the exposed showed a significant increase over the same period of time. SCE frequency in the exposed population was significantly different from controls.

Adult↗
PubMed1995

Comparative studies of two organophosphorus compounds in the mouse.

A rodent model, the albino mouse, was used to investigate the in vitro and in vivo capacity of 2 organophosphate (OP) compounds, mipafox and ecothiopate, to inhibit enzymes considered to be involved in the mechanisms of OP toxicity. Mipafox and ecothiopate were chosen as model compounds because the former can produce a delayed neuropathy whereas the latter does not. Mipafox (110 mumol/kg, s.c.) inhibited brain acetylcholinesterase (AChE), neuropathy target esterase (NTE) and phenylvalerate hydrolases by 58, 64 and 65%, while diaphragm AChE and phenylvalerate hydrolases were inhibited by 66 and 80%, respectively. In contrast, ecothiopate (0.5 mumol/kg) had no effect on brain NTE or on brain or diaphragm phenylvalerate hydrolases. At the same time, diaphragm AChE was inhibited by 60% while brain AChE activity had increased by 15% of control. Mipafox was a potent inhibitor of AChE and NTE in vitro. Although ecothiopate was a highly potent anti-ChE in vitro, it had no inhibitory effect on NTE.

Analysis of Variance↗
PubMed1995

Neutrophil chemoattractants generated in two phases during reperfusion of ischemic myocardium in the rabbit. Evidence for a role for C5a and interleukin-8.

The neutrophil chemoattractants generated in a model of myocardial infarction in the anesthetized rabbit were investigated. Coronary artery occlusion was followed by reperfusion for periods from 5 min to 4.5 h. Extracts of myocardial tissue in normal and post-ischemic zones were tested for C5a and interleukin-8 (IL-8) using specific radioimmunoassays. In the post-ischemic zone, immunoreactive C5a was detected within 5 min and rose progressively to reach a plateau at 3-4.5 h. In contrast, immunoreactive IL-8 concentrations rose after a delay and were highest at the last time point tested, 4.5 h. Myeloperoxidase activity levels, an index of neutrophil accumulation, rose progressively as the concentrations of chemoattractants increased. Using cation exchange and reversed phase HPLC, immunoreactive C5a and IL-8 co-eluted with authentic standards. Fractions taken at the C5a and IL-8 peaks from reversed phase HPLC exhibited neutrophil aggregating activity which was neutralized by the respective antibody used in the radioimmunoassays. Depletion of circulating neutrophils virtually abolished immunoreactive IL-8 in the post-ischemic myocardial tissue. These observations suggest a sequential release of chemoattractants: the first, C5a is generated in interstitial fluid, followed by IL-8 generated by infiltrating neutrophils. Thus, over the time period studied, IL-8 generation would be expected to be indirectly dependent on C5a production.

Animals↗
PubMed1994

Isolation of a hamster cDNA clone coding for a function involved in methotrexate uptake.

A clone has been isolated from a Chinese hamster ovary cell cDNA expression library that complements mutant cells defective in the uptake of the folate analogue methotrexate. When transfected with this clone, the mutant cells regain the ability to bind and transport the drug and, as a consequence, become sensitive to its cytotoxic action. The clone is 2314 base pairs long and has an open reading frame of 1557 base pairs that codes for a putative protein of 58 kDa. This novel putative protein has a high content of hydrophobic residues and has a large part of its predicted secondary structure in the form of beta-sheets. In the wild-type cell line and in one of the mutant cell lines, this clone detects an mRNA of 2.5 kilobases, while in another mutant cell line, this message is absent. The data are consistent with this clone encoding either the reduced folate transporter or an auxiliary function that interacts with this transporter. This is the first report of a cDNA coding for a function, other than folate-binding protein, that is involved in the transport of methotrexate.

ATP Binding Cassette Transporter, Subfamily G, Mem↗
PubMed1994

Electrophysiological and biochemical effects following single doses of organophosphates in the mouse.

Single doses of organophosphates (mipafox or ecothiopate) were given subcutaneously to mice. At intervals up to 77 days after dosing animals were killed and muscle action potentials and endplate potentials were recorded intracellularly in mouse phrenic-nerve/hemidiaphragm preparations. Activities of acetylcholinesterase and neuropathy target esterase in brain and acetylcholinesterase in diaphragm were also measured. Mipafox (0.11 mmol/kg), a neurotoxic organophosphate, produced an increase in prejunctional jitter (i.e. the variabilities of the latencies) of endplate potentials. This increase began 14-21 days after administration and lasted more than 23 days. No clinical signs of neuropathy were observed during this study. Mipafox also produced an increase in postjunctional (muscle action potential) jitter. Mipafox inhibited brain and diaphragm acetylcholinesterase and brain neuropathy target esterase. By comparison, a non-neurotoxic organophosphate, ecothiopate (0.5 mumol/kg), was a potent inhibitor of diaphragm acetylcholinesterase and produced a large increase in postjunctional jitter but ecothiopate did not inhibit brain neuropathy target esterase and had no effect on prejunctional jitter. Doses were chosen so that the inhibition of diaphragm acetylcholinesterase by each of the two organophosphates was similar. It is concluded that the neurotoxic organophosphate, mipafox, produced measurable changes in nerve function. These long-term changes may represent a new phenomenon, unrelated to the classical organophosphate induced delayed neuropathy. Alternatively, they may represent a neuropathic process which precedes or is below the threshold for clinical signs.

Acetylcholinesterase↗
PubMed1994

Role of CD18 in the accumulation of eosinophils and neutrophils and local oedema formation in inflammatory reactions in guinea-pig skin.

1. Intradermal injection of the complement fragment C5a des Arg induces local oedema formation that, in rabbits and man, is dependent on circulating neutrophils. Monoclonal antibodies to the leukocyte adhesion molecule CD11/CD18 block neutrophil accumulation and prevent neutrophil-dependent oedema formation. The role of CD11/CD18 in mediating eosinophil accumulation in vivo is less established. In this study we have used an anti-human CD18 monoclonal antibody, 6.5E, to investigate the neutrophil-dependency of oedema formation induced by C5a des Arg in guinea-pig skin. We also studied the role of CD18 in mediating eosinophil accumulation in the same model. 2. Stimulated adhesion of 111In-labelled guinea-pig neutrophils and eosinophils to serum-coated plastic was inhibited in a dose-dependent manner by 6.5E suggesting that the monoclonal antibody recognizes and blocks the guinea-pig CD18 adhesion molecule. 3. The accumulation of 111In-labelled neutrophils induced by zymosan-activated plasma (ZAP, as a source of C5a des Arg) in skin sites was reduced by up to 89% in animals treated intravenously with F(ab')2 fragments of 6.5E. ZAP-induced accumulation of 111In-labelled eosinophils was also greatly reduced (by up to 78%) by treatment with 6.5E. 4. Despite the inhibition of ZAP-induced neutrophil accumulation by 6.5E, local oedema formation in the same skin sites was unaffected, except at the top dose of ZAP, by treatment with the anti-CD18 monoclonal antibody, suggesting that the oedema response was largely neutrophil-independent. Indeed, ZAP-induced oedema formation was reduced by up to 81% by the H1 receptor antagonist, mepyramine. 5. Accumulation of 111 In-labelled eosinophils in a passive cutaneous anaphylactic (PCA) reaction was also blocked by treatment with 6.5E, while oedema formation in the same skin sites was unaffected.Intradermal injection of cationic protein-containing extracts of Schistosoma mansoni larvae also induced the accumulation of 111 In-labelled neutrophils and eosinophils which was abrogated by intravenous 6.5E.In contrast, extract-induced local oedema formation was similar in control and 6.5E-treated guinea-pigs.6. In summary, the local accumulation of radiolabelled neutrophils at sites of inflammation in guinea pigskin was dependent on the adhesion molecule CD18 while, in contrast, there was no evidence for neutrophil-dependent oedema formation in this species. Accumulation of radiolabelled eosinophils was also dependent on CD18.

Animals↗
PubMed1994

Effect of duration of ischaemia on reduction of myocardial infarct size by inhibition of neutrophil accumulation using an anti-CD18 monoclonal antibody.

1. Neutrophil accumulation is a characteristic feature of the inflammatory response in myocardial tissue which has undergone a period of ischaemia. The aim of this study was to examine whether inhibition of myocardial neutrophil infiltration, using an antibody to the CD18 leukocyte adhesion molecule, was effective in reducing infarct size in anaesthetized rabbits. 2. Anaesthetized rabbits underwent coronary artery occlusion (CAO) for periods of 30 or 45 min followed by reperfusion for 3 h. Animals were treated intravenously 10 min prior to reperfusion with IB4, a monoclonal antibody to CD18 (1 mg kg-1) or saline (1 ml kg-1). In one group undergoing 45 min CAO, a control antibody, OKMI (1 mg kg-1) was given. 3. Following either 30 or 45 min of CAO, administration of IB4 resulted in a < 75% inhibition in neutrophil accumulation in the area at risk myocardium (AR) compared with control animals. 4. With the 30 min occlusion period, IB4 significantly reduced myocardial infarct size, 27.2 +/- 3.2% vs 67.4 +/- 5.6% in the saline control group (n = 5 P < 0.01). In contrast, IB4 did not reduce infarct size following a 45 min period of ischaemia. 5. In the same animals administration of IB4 significantly inhibited oedema formation in skin elicited by intradermal administration of the neutrophil chemoattractant f-Met-Leu-Phe, but had no effect on coronary microvascular plasma protein leakage in the AR. 6. Our results indicate that infiltrating neutrophils exacerbate tissue injury following a relatively short, 30 min period of myocardial ischaemia in the rabbit. However, protection with IB4 was no longer seen if the period of CAO was extended to 45 min. The results in this model suggest neutrophils are not a major determinant of tissue injury following more than a very short period of ischaemia.

Animals↗
PubMed1993

Human xenobiotic metabolizing esterases in liver and blood.

Esterases in human liver microsomes hydrolysed fluazifop-butyl (Vmax 9.8 +/- 1.6 mumol/min/g tissue), paraoxon (Vmax 47.4 +/- 7.5 nmol/min/g tissue) and phenylacetate (Vmax 57 +/- 8 mumol/min/g tissue), whereas esterases found in the human liver cytosol hydrolysed fluazifop-butyl (Vmax 10.0 +/- 0.5 mumol/min/g tissue) and phenylacetate (Vmax 37 +/- 2.9 mumol/min/g tissue) but not paraoxon. Human plasma esterase hydrolysed fluazifop-butyl (Vmax 0.09 +/- 0.006 mumol/min/mL), paraoxon (Vmax 210 +/- 14 nmol/min/mL) and phenylacetate (Vmax 250 +/- 17 mumol/min/mL). Inhibitory studies using paraoxon, bis-nitrophenol phosphate and mercuric chloride indicated fluazifop-butyl hydrolysis involved carboxylesterase in liver microsomes and cytosol, and cholinesterase and carboxylesterase in plasma. Phenylacetate hydrolysis involved arylesterase in plasma, both arylesterase and carboxylesterase in liver microsomes and carboxylesterase in liver cytosol. Plasma hydrolysis is less important and overall esterase activity is lower in humans than in the rat which is therefore a poor model.

Adult↗
PubMed1993

Nature and role of xenobiotic metabolizing esterases in rat liver, lung, skin and blood.

In the present study, the distribution and nature of esterases in the rat which hydrolysed fluazifop-butyl, carbaryl, paraoxon and phenylacetate were investigated. Vmax and Km values for the hydrolysis reactions were determined. Fluazifop-butyl was hydrolysed to fluazifop by rat liver (Vmax mumol/min/g microsomes 6.2 +/- 0.4; cytosol 6.84 +/- 0.85), lung (Vmax microsomes 0.38 +/- 0.1; cytosol 1.5 +/- 0.32) and skin (Vmax microsomes 0.02 +/- 0.0015; cytosol 0.4 +/- 0.06) and by plasma (Vmax mumol/min/mL 5.8 +/- 0.48) and red blood cells (Vmax 0.03 +/- 0.015). Significant inhibition by paraoxon and bismitrophenol phosphate indicated the involvement of carboxylesterases. Carbaryl was hydrolysed by liver, lung and skin at a lower rate by microsomal fractions (Vmax nmol/min/g 2.1 +/- 0.25, 1.6 +/- 0.25, 0.2 +/- 0.035, respectively) compared to cytosolic fractions (Vmax 6.7 +/- 0.75, 1.4 +/- 0.36, 0.5 +/- 0.12) and plasma (Vmax nmol/min/mL 3.0 +/- 0.25). Hydrolysis involved carboxylesterases. Paraoxon was hydrolysed by paraoxonases/arylesterases only in the plasma (Vmax nmol/min/mL 246 +/- 12) and microsomal fractions from liver (Vmax 330 nmol/min/g +/- 25) and lung (Vmax 2 +/- 0.25). Phenylacetate was hydrolysed by both microsomal and cytosolic fractions from all tissues studied. Hydrolysis involved arylesterases in the microsomes and carboxylesterases in the cytosol. Extrahepatic hydrolysis may be important following some routes of exposure to xenobiotic esters.

Animals↗
PubMed1993

Pericyte mitogenic activity is reduced in the blood of type 1 diabetic patients with and without retinopathy.

Selective loss of capillary pericytes occurs early and specifically in diabetic retinopathy. We have investigated whether blood derivatives from patients with long-term type 1 (insulin-dependent) diabetes and no retinopathy differ from those with retinopathy and/or non-diabetic controls in their ability to stimulate DNA synthesis in cultured bovine retinal pericytes and endothelial cells. As a general trend, whole blood serum, platelet-rich plasma and platelet-free plasma from patients without and with retinopathy stimulated thymidine incorporation in both cell types less than derivatives from controls. Serum, 0.1% v/v final concentration in culture medium, from patients without retinopathy was less active (114.5 +/- 24.5% of a standard stimulus produced by 0.1% fetal calf serum) than that from patients with the complication (132.6 +/- 20.8%, P = 0.003) and both were less potent than control sera (143.6 +/- 28.0%, P < 0.001 and P = 0.013, respectively). Lack of support from circulating factor(s) may contribute to the disappearance of pericytes from the capillary wall in diabetes but further investigations are necessary to clarify the mechanisms that prevent the development of microangiopathy in some patients.

Adult↗