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Biomedical subjects

G W Taylor

Publications and source records attributed to G W Taylor.

At least 73 records · Page 4Linked to original sources
PubMed1996

Excursions in biomedical mass spectrometry.

1. Mass spectrometry (MS) has played a vital role in the research of the department of clinical pharmacology for over 25 years. 2. MS has been used for trace analysis of endogenous compounds and xenobiotics in plasma and urine, and also for a wide range of structural studies. 3. Examples of current applications are reported, including data from gas chromatography-mass spectrometry (GC-MS) assays for mevalonic acid, the identification of an antibiotic produced by Pseudomonas aeruginosa which is active against Helicobacter pylori, high pressure liquid chromatography (h.p.l.c)-electropray MS studies on steroid sulphates, the aspergillus ciliotoxin, gliotoxin, and ADP ribosyltransferase activity in human polymorphonuclear neutrophil leucocytes (PMNs). The value of electrospray MS in the molecular weight determination of proteins is exemplified by the analysis of human serum amyloid component P.

Anti-Bacterial Agents↗
PubMed1996

A possible role for mono (ADP-ribosyl) transferase in the signalling pathway mediating neutrophil chemotaxis.

1. Mono(ADP-ribosyl)transferase activity has been identified on the external surface of human polymorphonuclear neutrophil leucocytes (PMNs). The enzyme is released from the plasma membrane by phosphoinositide-specific phospholipase C, suggesting a glycosylphosphatidylinositol (GPI) linkage of the enzyme to the plasma membrane. Partial sequence of cDNA encoding the enzyme suggests that it is identical to the GPI-linked mono(ADP-ribosyl)-transferase identified previously on human skeletal muscle. 2. A panel of inhibitors of mono(ADP-ribosyl)transferase (including vitamins K1 and K3, novobiocin and nicotinamide) showed a rank order of inhibitory potency similar to that described for other mono(ADP-ribosyl)transferases. Furthermore, the mono(ADP-ribosyl)ation of agmatine was inhibited also by diethylamino (benzylidineamino)guanidine (DEA-BAG), another substrate of the enzyme related structurally to arginine. 3. There was a close linear correlation between the IC50 values for inhibition of mono(ADP-ribosyl)ation of agmatine by DEA-BAG or the enzyme inhibitors and their IC50 values for inhibition of receptor-dependent polymerization of cytoskeletal actin and chemotaxis. 4. These results suggest a role for mono(ADP-ribosyl)transferase in the transduction pathway involved in receptor-dependent re-alignment of the cytoskeleton during neutrophil chemotaxis.

ADP Ribose Transferases↗
PubMed1996

Acute hyperinsulinaemia decreases cholesterol synthesis less in subjects with non-insulin-dependent diabetes mellitus than in non-diabetic subjects.

To investigate the effect of insulin on cholesterol synthesis in vivo we measured plasma mevalonic acid (MVA) concentrations using gas chromatography-mass spectrometry in six non-obese patients with non-insulin-dependent diabetes mellitus (NIDDM) [four men, two women; age 57.5 +/- 2.2 years (mean +/- SEM); glycated haemoglobin (HbA1) 8.5 +/- 0.5%; total cholesterol (TC) 5.7 +/- 0.5 mmol L-1, triglyceride (TG) 3.8 +/- 0.9 mmol L-1] and six non-diabetic, sex- and age-matched control subjects (age 55.7 +/- 2.8 years; HbA1 6.5 +/- 0.1%; TC 5.4 +/- 0.3 mmol L-1, TG 1.2 +/- 0.1 mmol L-1). Subjects were studied twice: during 13-h hyperinsulinaemic (1 mu kg-1 min-1), euglycaemic (5 mmol L-1) clamp and during a saline infusion. Baseline MVA concentration was significantly higher in diabetic patients than in control subjects (9.8 +/- 0.7 ng mL-1 vs. 5.6 +/- 0.9 ng mL-1, P = 0.004). At the end of each study, MVA concentration, expressed as a percentage of baseline, was significantly lower during the hyperinsulinaemic, euglycaemic clamp than during the saline study in both the diabetic (54.4 +/- 5.3% vs. 69.6 +/- 6.3%, P = 0.036) and control subjects (30.5 +/- 3.4% vs. 61.7 +/- 6.0%, P = 0.01). However, the decrease in MVA during the hyperinsulinaemic clamp study was more marked in the control subjects than in the diabetic subjects (P = 0.03). A significant positive correlation was found between percentage decrease of MVA and non-esterified fatty acids following the insulin clamp in NIDDM (r = 0.83, P = 0.04). We conclude that acute hyperinsulinaemia decreases cholesterol synthesis less in subjects with NIDDM than in non-diabetic subjects and that this phenomenon, together with increased basal cholesterol synthesis in NIDDM, may in part be due to insulin resistance.

Analysis of Variance↗
PubMed1996

Severe periodontitis and risk for poor glycemic control in patients with non-insulin-dependent diabetes mellitus.

This study tested the hypothesis that severe periodontitis in persons with non-insulin-dependent diabetes mellitus (NIDDM) increases the risk of poor glycemic control. Data from the longitudinal study of residents of the Gila River Indian Community were analyzed for dentate subjects aged 18 to 67, comprising all those: 1) diagnosed at baseline with NIDDM (at least 200 mg/dL plasma glucose after a 2-hour oral glucose tolerance test); 2) with baseline glycosylated hemoglobin (HbA1) less than 9%; and 3) who remained dentate during the 2-year follow-up period. Medical and dental examinations were conducted at 2-year intervals. Severe periodontitis was specified two ways for separate analyses: 1) as baseline periodontal attachment loss of 6 mm or more on at least one index tooth; and 2) baseline radiographic bone loss of 50% or more on at least one tooth. Clinical data for loss of periodontal attachment were available for 80 subjects who had at least one follow-up examination, 9 of whom had two follow-up examinations at 2-year intervals after baseline. Radiographic bone loss data were available for 88 subjects who had at least one follow-up examination, 17 of whom had two follow-up examinations. Poor glycemic control was specified as the presence of HbA, of 9% or more at follow-up. To increase the sample size, observations from baseline to second examination and from second to third examinations were combined. To control for non-independence of observations, generalized estimating equations (GEE) were used for regression modeling. Severe periodontitis at baseline was associated with increased risk of poor glycemic control at follow-up. Other statistically significant covariates in the GEE models were: 1) baseline age; 2) level of glycemic control at baseline; 3) having more severe NIDDM at baseline; 4) duration of NIDDM; and 5) smoking at baseline. These results support considering severe periodontitis as a risk factor for poor glycemic control and suggest that physicians treating patients with NIDDM should be alert to the signs of severe periodontitis in managing NIDDM.

Adolescent↗
PubMed1995

Formation and metabolism of 14,15-epoxyeicosatrienoic acid by human reproductive tissues.

Human granulosa-luteal cells cultured in the presence of arachidonic acid produced low levels of the epoxygenase metabolite 14,15-epoxy-5,8,11-(Z,Z,Z)-eicosatrienoic acid (14,15-EpETrE) as determined by HPLC analysis and gas chromatography mass spectrometry. When authentic 14,15-[3H]EpETrE was incubated with these cells in the absence of serum it was metabolised initially to the dihydroxy derivative (14,15-dihydroxy-5,8,11-eicosatrienoic acid, 14,15-DiHETrE) and subsequently to a number of more polar metabolites as determined by HPLC. Fetal calf serum protected 14,15-EpETrE from metabolism for at least 2 h. A similar pattern of metabolism was obtained when 14,15-[3H]EpETrE was incubated with a human choriocarcinoma cell line (BeWo). Microsomes from this cell line converted arachidonic acid to a large number of radioactive metabolites including 14,15-DiHETrE and 11,12-DiHETrE although there was no evidence for the parent epoxides. These results extend earlier findings that human reproductive tissues produce epoxygenase metabolites, and demonstrate the rapid metabolism of these compounds by intact cells in the absence of serum.

8,11,14-Eicosatrienoic Acid↗
PubMed1995

The proximal pathway of metabolism of the chlorinated signal molecule differentiation-inducing factor-1 (DIF-1) in the cellular slime mould Dictyostelium.

Stalk cell differentiation during development of the slime mould Dictyostelium is induced by a chlorinated alkyl phenone called differentiation-inducing factor-1 (DIF-1). Inactivation of DIF-1 is likely to be a key element in the DIF-1 signalling system, and we have shown previously that this is accomplished by a dedicated metabolic pathway involving up to 12 unidentified metabolites. We report here the structure of the first four metabolites produced from DIF-1, as deduced by m.s., n.m.r. and chemical synthesis. The structures of these compounds show that the first step in metabolism is a dechlorination of the phenolic ring, producing DIF metabolite 1 (DM1). DM1 is identical with the previously known minor DIF activity, DIF-3. DIF-3 is then metabolized by three successive oxidations of its aliphatic side chain: a hydroxylation at omega-2 to produce DM2, oxidation of the hydroxy group to a ketone group to produce DM3 and a further hydroxylation at omega-1 to produce DM4, a hydroxyketone of DIF-3. We have investigated the enzymology of DIF-1 metabolism. It is already known that the first step, to produce DIF-3, is catalysed by a novel dechlorinase. The enzyme activity responsible for the first side-chain oxidation (DIF-3 hydroxylase) was detected by incubating [3H]DIF-3 with cell-free extracts and resolving the reaction products by t.l.c. DIF-3 hydroxylase has many of the properties of a cytochrome P-450. It is membrane-bound and uses NADPH as co-substrate. It is also inhibited by CO, the classic cytochrome P-450 inhibitor, and by several other cytochrome P-450 inhibitors, as well as by diphenyliodonium chloride, an inhibitor of cytochrome P-450 reductase. DIF-3 hydroxylase is highly specific for DIF-3: other closely related compounds do not compete for the activity at 100-fold molar excess, with the exception of the DIF-3 analogue lacking the chlorine atom. The Km for DIF-3 of 47 nM is consistent with this enzyme being responsible for DIF-3 metabolism in vivo. The two further oxidations necessary to produce DM4 are also performed in vitro by similar enzyme activities. One of the inhibitors of DIF-3 hydroxylase, ancymidol (IC50 67 nM) is likely to be particularly suitable for probing the function of DIF metabolism during development.

Animals↗
PubMed1995

Rapid identification of 4-hydroxy-2-alkylquinolines produced by Pseudomonas aeruginosa using gas chromatography-electron-capture mass spectrometry.

The 4-hydroxy-2-alkylquinolines and their N-oxides are secondary metabolites produced by Pseudomonas aeruginosa which inhibit the growth of a number of Gram-positive organisms including Staphylococcus aureus. To facilitate the identification of these compounds in biological fluids, we have developed a rapid profiling system based on gas chromatography-electron-capture mass spectrometry of the O-bistrifluoromethylbenzoyl derivatives. Using the technique, over twenty hydroxyalkylquinolines have been identified from a culture obtained from a strain of P. aeruginosa obtained from a patient with severe bronchiectasis.

Bronchiectasis↗
PubMed1995

Role of metabotropic glutamate receptor subtypes in the patterning of epileptiform activities in vitro.

1. Epileptiform activities were elicited from the in vitro guinea pig hippocampus by the addition of picrotoxin. Modification of the picrotoxin-induced activities by agents active at metabotropic glutamate receptors (mGluRs) was examined using intracellular and extracellular recordings. 2. Picrotoxin typically elicited synchronized discharges (epileptiform bursts) in CA3 neurons. These spontaneously occurred at regular intervals. In the presence of (+)-alpha-methyl-4-carboxyphenylglycine (MCPG; 700-1,000 microM), an antagonist at multiple mGluR subtypes, the frequency of spontaneous epileptiform bursts decreased. In contrast, when the mGluR agonists (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid (ACPD; 5 microM) or (2S,3S,4S)-alpha-(carboxycyclopropyl)-glycine (L-CCG-I; 10 microM) were added to the incubating medium, the frequency of epileptiform bursts increased. No consistent change in membrane potential, burst duration, nor burst afterhyperpolarization was associated with the changes in burst frequency. 3. When spontaneous burst frequency was reduced in MCPG, stimulation at a higher frequency entrained bursts without failure. Bursts evoked in MCPG were similar in waveform and amplitude to those evoked in the control state. 4. (S)-4-carboxyphenylglycine (S-4CPG) and (R,S)-4-carboxy-3-hydroxyphenylglycine (RS-4C3HPG) are antagonists at mGluR subtypes 1 and 5 but agonists at mGluRs 2 and 3. Addition of either of these agents increased the frequency of epileptiform bursts. 5. These results suggest that sufficient glutamate is released during epileptiform activities to activate mGluRs. The overall effect is to increase the frequency of synchronized discharges. This modulatory action on burst frequency is probably mediated via the mGluR 2 and 3 receptor subclass.

Animals↗
PubMed1995

Synchronized oscillations in hippocampal CA3 neurons induced by metabotropic glutamate receptor activation.

The metabotropic glutamate receptor agonist (1S,3R)-1-aminocyclopentane-1,3 dicarboxylic acid (ACPD) at concentrations above 60 microM produced stereotypic oscillatory activity in CA3 pyramidal cells of rat hippocampal slices. This oscillatory activity consisted of trains of depolarizations with overriding action potentials. On average, individual trains lasted 7 sec and recurred at intervals of 24 sec. During each train, the constituent depolarizations achieved a maximum frequency of 27 Hz, then slowed to 8 Hz toward the end of the train. Extracellular and dual intracellular recordings suggested that this ACPD-induced oscillatory activity occurred synchronously in the CA3 population. The oscillations persisted in the presence of GABAA, GABAB, and NMDA receptor antagonists. In contrast, the oscillations were blocked by the AMPA/kainate receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX; 10-30 microM). Likewise, the oscillations were blocked by the metabotropic glutamate receptor antagonists (+)-alpha-methyl-4-carboxyphenylglycine [(+)-MCPG; 1 mM], (S)-4-carboxy-3-hydroxyphenylglycine [(S)-4C3HPG; 1mM] and (S)-4-carboxyphenylglycine [(S)-4CPG; 1 mM]. The results suggest that activation of metabotropic glutamate receptors can result in a permissive state that allows AMPA/kainate receptor-mediated conductances to mediate synchronized activity among hippocampal CA3 neurons.

Animals↗
PubMed1994

Neck strain in car occupants: injury status after 6 months and crash-related factors.

In this study, 29 individuals who sustained a neck strain as a result of a car crash were drawn from a group of physiotherapy and general practices and were followed up after 6 months. The aim was to examine relationships between the state of the neck injury at the time of follow up and crash-related factors, notably crash severity and occupant awareness. Crash severity was assessed by measurement of damage to the involved vehicles, while 6-month injury status was established through physical examinations and interviews. No statistically significant associations between crash severity and 6-month injury status were found, but subjects who were unaware of the impending collision had a greatly increased likelihood of experiencing persisting symptoms of and/or signs of neck strain, compared with those who were aware (odds ratio = 15.0; 95 per cent confidence limits: 1.8, 178). While the role of crash severity in the production and duration of neck strains remains unclear, awareness appears to have a strong protective influence and may prove to be a useful prognostic indicator in clinical settings.

Accidents, Traffic↗
PubMed1994

The effect of erythromycin on Pseudomonas aeruginosa and neutrophil mediated epithelial damage.

Erythromycin therapy for long periods may benefit patients with chronic bronchial sepsis colonized by Pseudomonas aeruginosa despite the lack of antibacterial activity. We have investigated the effect of filtrates of 24 h P. aeruginosa cultures (CF) with or without erythromycin 0.5, 5, 20 mg/L on human nasal epithelium in the absence or presence of polymorphonuclear leucocytes (PMN). Ciliary beat frequency (CBF) and epithelium integrity were examined for 4 h. Erythromycin (20 mg/L) alone did not affect epithelium. CF without erythromycin slowed CBF by 63.5% of control at 4 h, and caused disruption of surface integrity in 80% of the epithelium. Addition of erythromycin to CF did not inhibit these effects. Erythromycin did not affect growth of P. aeruginosa. Filtrates of P. aeruginosa cultured with erythromycin (5 and 20 mg/L) caused less CBF slowing (37.2% and 19.2% of control, respectively) and epithelial disruption (4.2% and 6.7%, respectively). Unstimulated PMN (10(7)/mL) slowed CBF by 13% of control at 4 h but did not cause epithelial disruption. PMN and CF together slowed CBF (95.4% of control) and damaged epithelium (93.3% of epithelium disrupted) synergically. Pre-incubation of PMN with erythromycin did not inhibit these effects. PMN and filtrates of P. aeruginosa cultured with erythromycin (5 and 20 mg/L) caused less CBF slowing (58.0% and 33.6% of control, respectively) and epithelial disruption (40.0% and 13.3%, respectively). Erythromycin may benefit patients by reducing P. aeruginosa production of factors which damage epithelium and stimulate neutrophil mediated cytotoxicity.

Bacterial Toxins↗
PubMed1994

Tumour necrosis factor-alpha and leukotriene E4 production in wheezy infants.

It is not clear why certain infants wheeze during viral upper respiratory tract infections (URTIs) but it is possible that they have a tendency to mount an exaggerated inflammatory response leading to production of mediators that induce airway narrowing. We studied nasal tumour necrosis factor-alpha (TNF alpha) and urinary leukotriene E4 (LTE4) production during infection and after recovery in 31 wheezy infants (median age 6.2 months). Urinary LTE4 production was not altered during wheezy episodes or URTIs. However, the concentration of TNF alpha in nasal lining fluid (NLF) was significantly increased during acute episodes of wheeze compared to recovery (median [interquartile range] of 293 [42-1753] vs 0 [0-203] pg/ml NLF). TNF alpha was detectable more often and in higher concentration when wheezing was due to respiratory syncytial virus. TNF alpha was also present in 7/30 asymptomatic wheezy infants who had recovered from infection (> 100 pg/ml NLF) and in 4/7 non-wheezy siblings during URTIs (> 200 pg/ml NLF). This suggests that upregulation of TNF alpha production is not the only factor that makes some infants wheeze.

Child, Preschool↗
PubMed1994

Effect of salmeterol on human nasal epithelial cell ciliary beating: inhibition of the ciliotoxin, pyocyanin.

1. Patients with airway infection by Pseudomonas aeruginosa have impaired mucociliary clearance. Pyocyanin is a phenazine pigment produced by P. aeruginosa which is present in the sputum of colonized patients, slows human ciliary beat frequency (CBF) in vitro and slows mucociliary transport in vivo in the guinea-pig. 2. We have investigated the effect of salmeterol, a long-acting beta 2-adrenoceptor agonist, on pyocyanin-induced slowing of human CBF in vitro. Salmeterol (2 x 10(-7) M) was found to reduce pyocycanin (20 micrograms ml-1)-induced slowing of CBF by 53% and the fall in intracellular adenosine 3':5'-cyclic monophosphate (cyclic AMP) by 26% and ATP by 29%. 3. Another beta 2-adrenoceptor agonist, isoprenaline (2 x 10(-7) M), also inhibited pyocyanin-induced slowing of CBF by 39%. 4. The effects of salmeterol (30 min preincubation) persisted after washing the cells. 5. Propranolol (10(-7) M) and the beta 2-specific antagonist, ICI 118551 (10(-6) M) blocked the protective effects of salmeterol completely, but atenolol (10(-6) M) was less effective. These results suggested that the effects of salmeterol on pyocyanin-induced effects were mediated primarily via the stimulation of beta 2-adrenoceptors. 6. Pyocyanin-induced ciliary slowing is associated with a substantial fall in intracellular cyclic AMP and ATP. Salmeterol reversed the effects of pyocyanin on cyclic AMP and ATP. 7. Mucociliary clearance is an important defence mechanism of the airways against bacterial infection. Salmeterol may benefit patients colonized by P. aeruginosa, not only by its bronchodilator action, but also by protecting epithelial cells from pyocyanin-induced slowing of CBF.

Adenosine Triphosphate↗
PubMed1994

Effect of tracheal cytotoxin from Bordetella pertussis on human neutrophil function in vitro.

The infiltration of neutrophils which phagocytose and kill microorganisms is an important defense mechanism against infections of the airways. Bordetella pertussis is a human respiratory pathogen which colonizes ciliated epithelium, causing whooping cough. We have investigated the effects of the peptidoglycan fragment tracheal cytotoxin (TCT) of B. pertussis on human neutrophil function in vitro. TCT (10(-6) to 10(-8) M) was toxic for human neutrophils, as measured by lactate dehydrogenase release and levels of intracellular ATP. TCT (10(-9) to 10(-15) M) did not stimulate neutrophil migration or chemiluminescence and did not affect neutrophil phagocytosis. Incubation of neutrophils for 20 min with TCT (10(-9) to 10(-11) M) significantly inhibited (P < 0.05) their subsequent migration toward the chemotactic factor N-formyl-L-methionyl-L-leucyl-L-phenylalanine (FMLP; 10(-9) M). Incubation of neutrophils for 20 min with TCT (10(-9) to 10(-15) M) significantly inhibited (P < 0.05) chemiluminescence stimulated by FMLP (10(-5) M). TCT (10(-6) to 10(-12) M) did not stimulate interleukin-1 alpha production by neutrophils or serum complement activation by the alternate pathway. We conclude that TCT at concentrations of < 10(-8) M affects important neutrophil functions and at higher concentrations is toxic. TCT may therefore contribute to the survival of B. pertussis within the airways in vivo.

Bordetella pertussis↗
PubMed1993

Neck strain in car occupants. The influence of crash-related factors on initial severity.

OBJECTIVE: To examine the relationship between the initial severity of neck strain in car occupants and crash-related factors, in particular, crash severity. DESIGN/PARTICIPANTS: Thirty-two individuals with neck strain after a car crash, drawn from physiotherapy and general practices in metropolitan Adelaide, were interviewed about their experience and examined by a manipulative physiotherapist. Crash severity was assessed by measurement of damage to the involved vehicles. MAIN OUTCOME MEASURES: Five measures of neck strain severity were obtained: number of body regions with symptoms, number of positive responses to palpation, cervical range of motion, subject's own rating on an analogue pain scale, and examiner's severity rating. Two measures of crash severity were used: maximum residual deformation, and velocity change of the subject's vehicle. RESULTS: Neck strain was observed in individuals who were involved in crashes of low severity. Maximum residual deformation of the vehicle was negatively associated with the subject's cervical range of motion and positively associated with the other measures of neck strain severity. For rear impacts, both measures of crash severity were associated with measures of neck strain severity. The group of subjects who were aware of the impending collision had a greater range of cervical spine movement and fewer positive responses to palpation than those who were unaware. CONCLUSIONS: Initial severity of neck strain is positively correlated with crash severity. Awareness of the impending collision may have a mitigating effect on injury severity.

Accidents, Traffic↗
PubMed1993

Metronidazole uptake by sensitive and resistant isolates of Helicobacter pylori.

The development of metronidazole resistance in Helicobacter pylori has become an important factor in the clinical use of this drug in the treatment of gastritis and peptic ulcers. The mechanism for the development of resistance is not known but may involve factors which influence metronidazole uptake and metabolism. In this study, a simple and reliable HPLC assay for metronidazole was developed and the uptake of the drug from broth cultures of both resistant and sensitive strains of H. pylori was investigated. Resistance to metronidazole was determined by the E test as well as plate and broth assays. In the presence of the antibiotic (approximately 10 mg/L), metronidazole-sensitive strains were killed within 24 h and there was a concomitant fall in the concentration of metronidazole in the broth. In contrast, the killing of resistant strains of H. pylori was associated with < 10% loss of antibiotic from broth. These differences in metronidazole uptake are ascribed to alterations in the mechanisms of action of the drug in sensitive and resistant strains.

Chromatography, High Pressure Liquid↗