Selective inhibition of mammalian lanosterol 14 alpha-demethylase: a possible strategy for cholesterol lowering.
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Aniline Compounds↗
Biomedical subjects
K A Walker
Publications and source records attributed to K A Walker.
Cigarette smoking, antioxidants, lipid peroxidation, and coronary heart disease.
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Aged↗
Stereoisomers of ketoconazole: preparation and biological activity.
The four stereoisomers of the antifungal agent ketoconazole (1) were prepared and evaluated for their selectivity in inhibiting a number of cytochrome P-450 enzymes. Large differences in selectivity among the isomers were observed for inhibition of the cytochromes P-450 involved in steroid biosynthesis, whereas little differences was observed for inhibition of those associated with hepatic drug metabolism. The cis-(2S,4R) isomer 2 was the most effective against rat lanosterol 14 alpha-demethylase, (2S,4R)-2 greater than (2R,4S)-4 much greater than (2R,4R)-3 = (2S,4S)-5, and progesterone 17 alpha,20-lyase, (2S,4R)-2 much greater than (2S,4S)-5 greater than (2R,4R)-3 = (2R,4S)-4, whereas the cis-(2R,4S) isomer 4 was more effective against cholesterol 7 alpha-hydroxylase, (2R,4S)-4 greater than (2S,4S)-5 greater than (2R,4R)-3, greater than (2S,4R)-2, and the trans-(2S,4S) isomer 5 was the most effective against aromatase, (2S,4R)-5 much greater than (2R,4R)-3 = (2R,4S)-4 greater than (2S,4R)-2. The cis-(2S,4R) and trans-(2R,4R) isomers 2 and 3 are equipotent in inhibiting corticoid 11 beta-hydroxylase and much more effective than their antipodes. Little selectivity was observed for inhibition of cholesterol side chain cleavage or xenobiotic hydroxylase. These data indicate that the affinity of azoles for cytochrome P-450 enzymes involved in steroid synthesis is highly dependent on the stereochemistry of the entire molecule, whereas binding to drug metabolizing enzymes is a less selective process.
Adrenal Glands↗
3,4-Dihydroquinolin-2(1H)-ones as combined inhibitors of thromboxane A2 synthase and cAMP phosphodiesterase.
A series of 1H-imidazol-1-yl- and 3-pyridyl-substituted 3,4-dihydroquinolin-2(1H)-ones was designed and synthesized as combined inhibitors of thromboxane (TXA2) synthase and cAMP phosphodiesterase (PDE) in human blood platelets. A number of structures, e.g. 4b, 7a, 7e, 13a, and 21-25, were superior to dazoxiben 26 as inhibitors of TXA2 synthase in in vitro ADP-induced aggregation experiments with human blood platelets. The TXA2 synthase inhibitory activity was confirmed by measurement of the prostanoid metabolites derived from 14C-labeled arachidonic acid. Three compounds (7a, 7e, and 25) demonstrated in vitro inhibition of human platelet cAMP PDE at micromolar concentrations in conjunction with their TXA2 synthase inhibitory activity. Synergistic enhancement of antiaggregatory and antithrombotic actions was expected when simultaneous stimulation of adenylate cyclase (through increased PGI2 production) and inhibition of platelet cAMP PDE were possible from the same compound. Ex vivo and in vivo experiments were conducted in rats and mice, respectively, to evaluate the effects of compounds 7e and 23 on platelet aggregation and thrombotic events within these animals. Compound 7e, which has a comparable level of TXA2 synthase (IC50 1.2 microM) and human platelet cAMP PDE (IC50 6.4 microM) inhibitory activities, was found to be orally bioavailable with a long duration of action and offered effective protection against mortality in a collagen-epinephrine-induced pulmonary thromboembolism model in mice. Significant blood pressure and heart rate effects were observed for several compounds, e.g. 7e, 9e, 13a, 13d, 18, 20, 21, and 23, when dosed orally in conscious spontaneously hypertensive rats.
3',5'-Cyclic-AMP Phosphodiesterases↗
Field trials of the Baby Check score card: mothers scoring their babies at home.
The Baby Check score card has been developed to help parents and health professionals grade the severity of acute illness in babies. This paper reports the results of two field trials in which mothers used Baby Check at home, 104 mothers scoring their babies daily for a week and 56 using it for six months. They all found Baby Check easy to use, between 68% and 81% found it useful, and 96% would recommended it to others. Over 70% of those using it daily used it very competently. Those using it infrequently did less well, suggesting that familiarity with the assessment is important. The scores obtained show that Baby Check's use would not increase the number of mothers seeking medical advice. With introduction and practice most mothers should be able to use Baby Check effectively. It should help them assess their babies' illnesses and make appropriate decisions about seeking medical advice.
Attitude↗
Field trials of the Baby Check score card in hospital.
The Baby Check score card was used by junior paediatric doctors to assess 262 babies under 6 months old presenting to hospital. The duty registrar and two consultants independently graded the severity of each baby's illness without knowledge of the Baby Check score. The registrars assessed the babies at presentation while the consultants reviewed the notes. The consultants and registrars agreed about the need for hospital admission only about 75% of the time. The score's sensitivity and predictive values were similar to those of the registrars' grading. The score's specificity was 87%. Babies with serious diagnosis scored high, while minor illnesses scored low. The predictive value for requiring hospital admission increased with the score, rising to 100% for scores of 20 or more. The appropriate use of Baby Check should improve the detection of serious illness. It could also reduce the number of babies admitted with minor illness, without putting them at increased risk.
Hospitalization↗
Tumor spheroid model for the biologically targeted radiotherapy of neuroblastoma micrometastases.
Neuroblastoma is a pediatric malignancy with a poor prognosis at least partly attributable to an early pattern of dissemination. New approaches to treatment of micrometastases include targeted radiotherapy using radiolabeled antibodies or molecules which are taken up preferentially by tumor cells. Multicellular tumor spheroids (MTS) resemble micrometastases during the avascular phase of their development. A human neuroblastoma cell line (NBl-G) was grown as MTS and incubated briefly with a radiolabeled monoclonal antibody (131I-UJ13A) directed against neuroectodermal antigens. Spheroid response was evaluated in terms of regrowth delay or proportion sterilized. A dose-response relationship was demonstrated in terms of 131I activity or duration of incubation. Control experiments using unlabeled UJ13A, radiolabeled nonspecific antibody (T2.10), radiolabeled human serum albumin, and radiolabeled sodium iodide showed these to be relatively ineffective compared to 131I-UJ13A. The cell line NBl-G grown as MTS has also been found to preferentially accumulate the radiolabeled catecholamine precursor molecule m-[131I]iodobenzylguanidine compared to cell lines derived from other tumor types. NBl-G cells grown as MTS provide a promising laboratory model for targeted radiotherapy of neuroblastoma micrometastases using radiolabeled antibodies or m-iodobenzylguanidine.
Antibodies, Monoclonal↗
Monomethyl ether derivatives of 7,8-dihydroxy- and 8,9-dihydroxy-4-n-propyl-1,2,3,4,4a,5,6,10b-octahydrobenzo[f]quinolines as possible products of metabolism by catechol-O-methyltransferase.
In order to facilitate identification of possible metabolites arising from in vitro action of catechol-O-methyltransferase upon 7,8-dihydroxy- and 8,9-dihydroxy-4-n-propyl-1,2,3,4,4a,5,6,10b-octahydrobenzo[f]quinolines (11, 12), all four possible monomethyl ether derivatives have been synthesized. Incubation of 11 and 12 with the enzyme revealed that the 8,9-dihydroxy positional isomer 12 (which contains the dopamine moiety held in the beta conformation) but not the 7,8-dihydroxy isomer 11 (which holds the dopamine moiety in the alpha conformation) was a substrate for the enzyme. The sole detectable product of 12 was 8-hydroxy-9-methoxy derivative 15 in which the "meta" hydroxy group of the dopamine moiety is etherified.
Animals↗
Distal tubular acidification in the remnant kidney.
The present studies examined the effect of three-fourths nephrectomy on the rate of acidification, i.e., total CO2 (tCO2) absorption (JtCO2) in the superficial distal tubule of the rat. Total glomerular filtration rate following three-fourths nephrectomy was 1.29 +/- 0.06 vs. 3.29 +/- 0.08 ml/min in sham controls, P less than 0.001. Systemic acid-base parameters were the same in both groups, but urine pH was lower in nephrectomized rats. In vivo microperfusion with identical isohydric solutions revealed that the JtCO2, fluid absorption (Jv), lumen-negative transepithelial potential difference (VT) were all significantly greater in the distal tubule of remnant kidneys. As the relative increase in Jv exceeded JtCO2, the perfusate tCO2 concentration increased markedly in remnant kidney distal tubules from 30.3 +/- 0.59 to 39.9 +/- 1.73 mM. To determine if the increase in tCO2 concentration accounted for the difference in JtCO2, a second control group was studied using a perfusate tCO2 concentration of 39.6 +/- 0.79 mM. Distal tubular JtCO2, Jv, and VT were significantly less in this control group than in the remnant kidney group. In separate studies, 10(-4) M amiloride was added to the perfusate used in remnant kidneys and controls studied with the elevated perfusate tCO2 concentration. The addition of 10(-4) M amiloride to the perfusate reduced VT and JtCO2. At identical values for VT, JtCO2 was higher in the distal tubule of remnant kidneys than in controls. We conclude the following. 1) The rate of acidification is increased in the distal tubule of remnant kidneys.(ABSTRACT TRUNCATED AT 250 WORDS)
Absorption↗
Delayed-onset muscle damage and lipid peroxidation in man after a downhill run.
Lipid peroxidation initiated by free radical reactions is associated with tissue necrosis in a variety of conditions. We have measured serum lipid peroxide concentrations (as total thiobarbituric acid-reactive substances, TBARS) and creatine kinase (CK), lactate dehydrogenase (LDH), and aspartate aminotransferase (AST) activities and subjective muscle soreness in 16 men before and after a 45-minute downhill treadmill run. TBARS concentrations and enzyme activities were increased after exercise, with peak values observed at 6 hours (TBARS, LDH) or 24 hours (CK, AST) after exercise. Serum LDH activity returned to preexercise levels by 48 hours after exercise and TBARS by 72 hours after exercise: CK and AST activities remained elevated 72 hours after exercise. Leg muscle soreness also increased, with the greatest degree of soreness seen at 24 or 48 hours after exercise. Subjects with the greatest increase in CK, LDH, and AST also showed the highest serum TBARS concentration. This suggests a possible relationship between free radical generation and exercise-induced muscle damage.
Adult↗
[(1H-imidazol-1-yl)methyl]- and [(3-pyridinyl)methyl]pyrroles as thromboxane synthetase inhibitors.
Several [(1H-imidazol-1-yl)methyl]- and [(3-pyridinyl)methyl] pyrroles were prepared and evaluated in vitro as thromboxane synthetase inhibitors in human platelet aggregation studies. A number of structures, e.g. 10b,f,g,i (respective IC50 values: 1 microM, 50 nM, 42 nM, 44 nM) showed superior in vitro inhibition of TXA2 synthetase when compared to the standard dazoxiben (1). However, it was found that in vitro potency did not translate into nor correlate with in vivo activity when these compounds were evaluated in mice in a collagen-epinephrine-induced pulmonary thromboembolism model. (E)-1-Methyl-2-[(1H-imidazol-1-yl)methyl]-5-(2-carboxyprop-1-enyl) pyrrole (10b) was found to offer protection against collagen-epinephrine-induced mortality in mice, thereby demonstrating that oral administration is an effective route for absorption of this drug. Additional evidence for the oral effectiveness of 10b in lowering serum TXB2 levels was obtained by performing ex vivo radioimmunoassay experiments with rats. A 13-week study of 10b in rats with reduced renal mass was conducted in order to evaluate the role of TXA2 production in hypertension and renal dysfunction. Although serum and urinary TXB2 levels in rats were found to be lowered during this study by 10b, the levels of urinary protein excretion remained comparable to that of the control group.
Animals↗
Effects of the selective herbicide fluazifop on fatty acid synthesis in pea (Pisum sativum) and barley (Hordeum vulgare).
Concentrations of fluazifop-butyl sprayed on intact plants caused large decreases in the incorporation of radioactivity from [1-14C]acetate into lipids of barley (Hordeum vulgare) leaves and stems, but did not affect leaves or stems of pea (Pisum sativum). Labelling of all acyl lipids, but not pigments, was reduced. The effects of the active acid form, fluazifop, were also determined in leaf pieces and chloroplasts. Concentrations of (R,S)-fluazifop up to 100 microM had no affect upon quality or quantity of fatty acids produced from [1-14C]acetate in pea. In barley, however, 100 microM-(R,S)-fluazifop caused 89% (leaf) or 100% (chloroplasts) inhibition in labelling of fatty acids from [1-14C]acetate. Lower concentrations of fluazifop (less than 25 microM) caused incomplete inhibition and significant decreases in the proportion of C18 fatty acids synthesized, particularly by isolated chloroplasts. Synthesis of fatty acids from [2-14C]malonate was also inhibited (59%) in barley leaf tissue by 100 microM-(R,S)-fluazifop. The labelling pattern of products showed that elongation reactions were unaffected by the herbicide, but synthesis de novo was specifically diminished. By using resolved stereoisomers, it was found that the (R) isomer was the form which inhibited fatty acid synthesis, a finding that is in agreement with its herbicidal activity. These results suggest that inhibition of fatty acid synthesis de novo forms the basis for the selective mode of action of fluazifop.
Acetates↗
Fluazifop, a grass-selective herbicide which inhibits acetyl-CoA carboxylase in sensitive plant species.
Fluazifop is a grass-selective herbicide that appears to act by inhibiting fatty acid synthesis de novo in sensitive species. Results from four different types of experiment show that this inhibition is due to an action of fluazifop on acetyl-CoA carboxylase and not on fatty acid synthetase. The acetyl-CoA carboxylase from sensitive barley (Hordeum vulgare), but not from resistant pea (Pisum sativum), is inhibited by the R stereoisomer, a finding that agrees with the herbicidal specificity of fluazifop.
Acetates↗
A tumour spheroid model for antibody-targeted therapy of micrometastases.
Human neuroblastoma cells grown as tumour spheroids were briefly incubated with a conjugate of 131I and an anti-human neuroectodermal monoclonal antibody UJ13A. Unbound 131I was removed by washing and the spheroids observed in culture conditions for up to 4 weeks. Spheroid response to irradiation was evaluated as time to reach 10x treatment volume and proportion of spheroids sterilised. Spheroid growth was found to be affected by both the activity of 131I-UJ13A and the duration of the incubation. Na[131I], 131I-HSA, 131I labelled non-specific antibody and unlabelled antibody were found to be relatively ineffective compared to 131I-UJ13A. The tumour spheroid model has applications in the evaluation of antibodies or antibody fragments and different radionuclides which may be considered for radioimmunotherapy of micrometastases.
Antibodies, Monoclonal↗
Detection of cytomegalovirus in shell vial cultures by using a DNA probe and early nuclear antigen monoclonal antibody.
An in situ biotinylated DNA probe assay was evaluated as an adjunct to anti-cytomegalovirus early nuclear antigen indirect immunofluorescence and cytopathic effect on cytomegalovirus-infected monolayers in shell vial cultures. Viral infection was detected by early nuclear antigen indirect immunofluorescence at 24 h and by DNA probe assay and shell vial cytopathic effect at 5 days.
Antibodies, Monoclonal↗
Total CO2 absorption in the distal tubule of the rat.
By use of in vivo microperfusion methodology, we assessed proton secretion (acidification) in the superficial distal tubule of the rat by determining the rate of total CO2 (tCO2) absorption (JtCO2). In these studies, we compared the JtCO2 in rats fed a diet that increased urine pH to the JtCO2 in rats fed a high-protein diet that reduced urine pH. The effect of amiloride added to the perfusate, used in rats fed the high-protein diet, was also examined. In rats, Group 1, fed a commercial diet, urine pH was 6.9; plasma tCO2 was 30.0 mM, and JtCO2 was 15.5 +/- 5.3 pmol X mm-1 X min-1. Following the ingestion of a high-protein diet the night before study, the urine pH fell to 5.6 and the plasma tCO2 to 28.2 mM. The JtCO2 in this group, Group 2, 41.1 +/- 4.8 was significantly greater than Group 1, P less than 0.05. The late distal transepithelial potential difference was comparable in both groups, -50.3 +/- 4.3 vs. -45.2 +/- 3.1 mV, P not significant. In a third group, Group 3, amiloride (10(-4) M) was added to the perfusate of rats prepared as in Group 2. JtCO2 was 23.4 +/- 0.4 pmol X mm-1 X min-1, significantly less than Group 2, P less than 0.05. The transepithelial potential difference was reduced to -4.0 +/- 2.3 mV, P less than 0.01 vs. Group 2. We conclude that the superficial distal tubule of the rat responds to subtle stimuli to increase proton secretion and contributes to urinary acidification. The rate of acidification can be influenced by alterations in the electrical profile across the acidifying epithelium.
Absorption↗
Radiofrequency (microwave) radiation exposure of mammalian cells during UV-induced DNA repair synthesis.
The effect of continuous-wave (CW) and pulsed-wave (PW) radiofrequency radiation (RFR) in the microwave range on UV-induced DNA repair has been investigated in MRC-5 normal human diploid fibroblasts. RFR exposure at power densities of 1 (or 5) and 10 mW/cm2 gave a maximum specific absorption rate (SAR) (at 10 mW/cm2) of 0.39 +/- 0.15 W/kg for 350 MHz RFR, 4.5 +/- 3.0 W/kg for 850 MHz RFR, and 2.7 +/- 1.6 W/kg for 1.2 GHz RFR. RFR exposures for 1 to 3 h at 37 degrees C, in either continuous-wave or pulsed-wave modes, had no effect on the rate of repair replication label incorporated into preexisting UV-damaged DNA. RFR exposures (PW), with a constant medium temperature of 39 degrees C at 350 and 850 MHz during the repair period after UV damage, also had no effect. Assay for induction of repair synthesis by RFR exposure alone in non-UV irradiated cells was negative for the 350-, 850-, and 1200-MHz CW and PW RFR at 37 degrees C and the 350- and 850-MHz PW RFR at 39 degrees C. RFR does not induce DNA repair under these exposure conditions. In preliminary experiments--with the tissue culture medium maintained at 39 degrees C and RFR exposures (PW) at the frequencies of 350, 850, and 1200 MHz--no effect on incorporation of [3H]thymidine into DNA undergoing semiconservative synthesis was observed.
Cell Line↗
Evidence for separate elongation enzymes for very-long-chain-fatty-acid synthesis in potato (Solanum tuberosum).
Aging potato (Solanum tuberosum) tuber discs in a Ca2+-containing medium resulted in increased rates of fatty acid labelling from [1-14C]acetate with time. Maximal labelling rates were seen after 6-8 h aging in a number of varieties. Saturated very-long-chain fatty acids (C20 and particularly C22 and C24) were very poorly labelled in freshly cut tissue. They were synthesized in increasing amounts and in a homologous sequence with progressive aging times. Use of increasing induction times and cycloheximide or puromycin as protein-synthesis inhibitors indicated that the sequence of fatty acid elongation was dependent on protein synthesis de novo and was controlled by three separate specific elongase enzymes.
Acetates↗