The mortality and humaneness of animal research on stress and pain.
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Animal Experimentation↗
Biomedical subjects
N E Miller
Publications and source records attributed to N E Miller.
Analogues of chloramphenicol as mechanism-based inactivators of rat liver cytochrome P-450: modifications of the propanediol side chain, the p-nitro group, and the dichloromethyl moiety.
The importance of the p-nitro group, the propanediol side chain, and the dichloromethyl moiety of chloramphenicol in regulating its effectiveness and selectivity as a mechanism-based inactivator of rat liver cytochromes P-450 has been examined. 1-p-Nitrophenyl-2-dichloroacetamidoethane, 1-p-nitrophenyl-2-dibromoacetamidoethane, and 1-phenyl-2-dichloroacetamidoethane were as effective as chloramphenicol at inactivating the major phenobarbital-inducible isozyme of rat liver cytochrome P-450, whereas 1-p-nitrophenyl-2-difluoroacetamidoethane caused no enzyme inactivation. Unlike chloramphenicol, 1-p-nitrophenyl-2-dichloroacetamidoethane and 1-phenyl-2-dichloroacetamidoethane also inactivated the major beta-naphthoflavone-inducible isozyme of rat liver cytochrome P-450. Alkaline hydrolysis of the adducts formed upon in vitro incubation of liver microsomes from phenobarbital- and beta-naphthoflavone-induced rats with [14C]-1-p-nitrophenyl-2-dichloroacetamidoethane resulted in the release of 4-nitro-1-phenethyl-1,2-dicarboxylic acid amide and oxalic acid. Enzymatic digests of the radio-labeled protein produced by incubation of a reconstituted system containing the major isozymes induced by beta-naphthoflavone or phenobarbital with [14C]-1-p-nitrophenyl-2-dichloroacetamidoethane led to the release of 4-nitro-1-phenethyl-1,2-dicarboxylic acid amide and 4-nitro-1-phenethyl oxamyl lysine. These results suggest that a single oxamyl chloride intermediate is responsible for the covalent modification and, hence, inactivation of both isozymes by 1-p-nitrophenyl-2-dichloroacetamidoethane.
Animals↗
Dichloromethyl compounds as mechanism-based inactivators of rat liver cytochromes P-450 in vitro.
Twenty dichloromethyl compounds have been tested as potential mechanism-based inactivators of the major phenobarbital-inducible isozyme of rat liver cytochrome P-450 (PB-B) in a reconstituted system. With the exception of dichloromethane and dichloroacetamide, all the compounds decreased the ethoxycoumarin deethylase activity of the enzyme in a time- and NADPH-dependent manner. The inhibitory compounds could be divided into two classes according to whether the loss of monooxygenase activity was accompanied by a decrease in spectrally detectable cytochrome P-450. N-Monosubstituted dichloroacetamides in which the side-chain consisted of a phenyl or n-octyl group were able to mimic the action of chloramphenicol and inactivate the PB-B without destroying the heme moiety. In contrast, dichloroacetamides containing an n-hexyl, n-butyl, or methyl substituent caused a significant loss of heme, as did the five non-amides tested: 1,1,2,2-tetrachloroethane, 1,1-dichloroacetone, methyl dichloroacetate, alpha,alpha-dichlorotoluene, and alpha,alpha-dichloroacetophenone. Representative compounds were also examined as inactivators of the major beta-naphthoflavone-inducible isozyme of rat liver cytochrome P-450 (BNF-B), using a reconstituted system, as well as of constitutive cytochromes P-450, using intact liver microsomes from untreated rats. These studies suggested a marked difference in isozyme selectivity between certain of the compounds. For example, of the isozymes monitored, only the PB-B was affected by alpha,alpha-dichlorotoluene in an NADPH-dependent manner, whereas N-octyl dichloroacetamide inactivated not only the PB-B and BNF-B, but also certain constitutive cytochromes, as evidenced by decreases in microsomal S-warfarin hydroxylase activities. These studies help delineate the structural requirements for the use of dichloromethyl compounds as probes of cytochrome P-450 function and as potential isozyme-selective inhibitors.
Acetamides↗
Evaluation of a commercial reagent for precipitating human serum low-density lipoprotein.
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Chemical Precipitation↗
On the mechanism of the inactivation of the major phenobarbital-inducible isozyme of rat liver cytochrome P-450 by chloramphenicol.
The mechanism of the inactivation of the major phenobarbital-inducible isozyme of rat liver cytochrome P-450 (P-450 PB-B2) by chloramphenicol has been investigated. Preparations of the enzyme from animals treated in vivo with chloramphenicol (CAP PB-B2) have been isolated, and their catalytic, spectral, and physical properties have been compared with those of the native PB-B2. The CAP PB-B2 exhibited: 1) a 60-70% loss in the rate of NADPH-supported monooxygenase activity with the substrates benzphetamine, 7-ethoxycoumarin, and p-nitroanisole; 2) a 60% decrease in the extent of enzymatic P-450 reduction catalyzed by NADPH-cytochrome P-450 reductase under both aerobic and anaerobic conditions; 3) a 60% decrease in the steady-state level of the ferrous dioxygen complex in the presence of substrates; 4) a 60% decrease in the magnitude of the type I spectral change induced by benzphetamine; and 5) a shift in the wavelength maximum for the chemically reduced ferrous-carbonyl complex from 450 to 451.5 nm. On the other hand, the ability of the CAP PB-B2 to catalyze the iodosobenzene-supported metabolism of 7-ethoxycoumarin and p-nitroanisole was unaltered. The results are consistent with a scheme whereby the binding of metabolites of chloramphenicol to amino acid residues in the PB-B2 close to the heme moiety blocks electron transport from NADPH-cytochrome P-450 reductase, thereby leading to a loss of monooxygenase activity.
7-Alkoxycoumarin O-Dealkylase↗
Are plasma lipoprotein cholesteryl esters utilized for biliary cholesterol and bile acid production in man?
Studies were carried out to determine whether or not plasma lipoprotein cholesteryl esters are available to the liver for biliary cholesterol and bile acid production in humans with intact biliary tracts. Six healthy males were given intravenous infusions of autologous high-density (d, 1.063-1.21; n = 2), low-density (d, 1.019-1.063; n = 2) or intermediate-density (d, 1.006-1.019; n = 2) lipoproteins that had been labelled in vitro with radioactive cholesteryl linoleate (n = 5) or cholesteryl oleate (n = 1). Duodenal contents were continuously aspirated via the intermediate and distal ports of a triple-lumen tube (mean recovery, 64 per cent), through the proximal port of which was infused an amino-acid solution. During 5-6 hours only moderate fluctuations were observed in bile acid and cholesterol secretion rates, implying the existence of near steady-state conditions. In all subjects radioactivity rapidly appeared in both biliary cholesterol and bile acids, and continued to be secreted for the duration of the experiment. The total radioactivity recovered from cholesterol averaged 0.27 per cent of the administered dose; the corresponding figure for bile acids was 11.2 per cent. These results indicate that lipoprotein cholesteryl esters are readily available for biliary lipid production in humans.
Adolescent↗
High-density lipoprotein composition is altered by a common DNA polymorphism adjacent to apoprotein AII gene in man.
25 of a group of 87 White men had Msp 1 restriction site polymorphism within an Alu sequence 3' to the human apo AII gene. Homozygosity for the polymorphism in 8 men was associated with a significant increase in serum apo AII levels (35.4 +/- 1.70 mg/dl, mean +/- SEM) and altered HDL composition, compared with heterozygotes (31.7 +/- 1.29; n = 17) and normal subjects (29.4 +/- 0.64; n = 62). This is the first account of a common variant of an HDL apoprotein gene that affects HDL composition. In view of its association with a high apo AII concentration homozygosity may protect against atherosclerosis.
Apolipoprotein A-I↗
An alternative procedure for incorporating radiolabelled cholesteryl ester into human plasma lipoproteins in vitro.
A simple method has been developed for labelling human plasma lipoproteins to high specific radioactivity with radioactive cholesteryl esters in vitro. After isolation by preparative ultracentrifugation, the selected lipoprotein was incubated for 30 min at 4 degrees C in human serum (d greater than 1.215) that had been prelabelled with [4-14C]cholesteryl oleate or [1,2-3H]cholesteryl linoleate, and was then re-isolated by ultracentrifugation. All major lipoprotein classes were labelled by the procedure. Specific radioactivities of up to 18 d.p.m. . pmol-1 (46 d.p.m. . ng-1) were achieved. When radiolabelled high-density lipoprotein was infused intravenously, the radioactive cholesteryl ester behaved in vivo indistinguishably from endogenous cholesteryl esters produced by the lecithin (phosphatidylcholine): cholesterol acyltransferase reaction.
Carbon Radioisotopes↗
Some professional and scientific problems and opportunities for biofeedback.
This paper will deal with a variety of topics such as dangers and opportunities from the developing crisis in health care costs, a cooperative study of the cost-effectiveness of treatments for headaches, the need for a federation of related societies, exploiting remarkable electronic advances, the wide range of adaptive functions of visceral learning (including its role in homeostasis), why maladjustments occur and their implications for biofeedback, and the need for analytic experiments involving adequate amounts of training.
Adaptation, Psychological↗
Relationship between changes in plasma lipoprotein concentrations and fecal steroid excretion in man during consumption of four experimental diets.
Limited information is available on the mechanism by which changes in nutrient intake influence plasma lipids. We compared the effects on plasma lipoprotein levels of 3 dietary modifications involving changes in total fat intake (27-40% of calories), cholesterol intake (100-250 mg/1000 kcal), the dietary polyunsaturated to saturated fatty acid ratio (0.3-1.0) and intake of vegetable-derived fiber and protein. On these 3 diets, plasma low density lipoprotein was reduced by 26-34%. Fecal bile acid excretion was similar on all diets (363-379 mg/day). There was no alteration in fecal bile acid output associated with an increase in polyunsaturated or total fat intake. Sterol balance became significantly more negative during consumption of only 1 of the 3 cholesterol-lowering diets. The observed reduction in plasma cholesterol levels was not associated with an increase in fecal bile acid output suggesting that diet-induced changes in circulating cholesterol are not maintained by an increase in sterol turnover but may reflect alterations in hepatic cholesterol and lipoprotein synthesis.
Adult↗
Energy expenditure in patients with low-, mid-, or high-thoracic paraplegia using Scott-Craig knee-ankle-foot orthoses.
Renewed interest in ambulation in patients with paraplegia prompted us to measure the energy expenditure (kcal/kg per min) during standing and ambulating with the Scott-Craig orthosis in nine patients who had low-, mid-, or high-thoracic paraplegia. Energy expenditure during standing and during ambulation with a walker was similar for patients with all levels of paraplegia. In patients with high-thoracic paraplegia, energy efficiency was significantly less (P less than 0.05) than that for patients with mid- or low-thoracic paraplegia, whose efficiency levels were similar. In patients with low-thoracic paraplegia, the only patients who could perform swing-through gait patterns, energy efficiency was increased because of increased velocity. Our data do not support the concept of denying, on the basis of the level of the lesion alone, young, otherwise healthy, well-motivated patients with thoracic paraplegia the opportunity of using Scott-Craig orthoses to supplement wheelchair mobility and activities of daily living.
Adolescent↗
The challenge of Alzheimer's disease.
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Aged↗
The value of behavioral research on animals.
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Agriculture↗
Behavioral method for the treatment of idiopathic scoliosis.
Idiopathic scoliosis was treated by an automated portable posture-training device that incorporated precise behavioral principles and enabled therapeutic training to be given in the patients' normal environment throughout the entire day. Twenty-one patient-years of training were completed with a group of 12 adolescent girls selected as being imminently likely to require a brace because of the way their spinal curves had been progressing. As an alternative to conventional brace therapy, patients found the posture-training device considerably less physically restraining and more cosmetically acceptable. Most patients wore it 23 hr per day for at least 1 year and adapted well to the constant physical and psychological presence of the instrument. For 10 patients, the outcome was entirely successful; they were discharged from this pilot study as satisfactorily corrected. Progression of the scoliotic curve was arrested; in fact, there was an average slight improvement in the Cobb angle (a measure of spinal curvature) as measured by x-ray radiography.
Adolescent↗
Leg braces: efficiency and energy expenditure.
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Adolescent↗
Plasma lipoproteins, antihypertensive drugs and coronary heart disease.
There is now a large body of evidence that susceptibility to coronary atherosclerosis is inversely related to the plasma high-density lipoprotein (HDL) cholesterol concentration, in addition to being directly related to blood pressure and the plasma low-density lipoprotein (LDL) level. Studies of the effects of drugs on coronary disease in humans and on experimental atherosclerosis in animals have provided evidence that the associations with HDL and LDL are causal, reflecting an atherogenic effect of one lipoprotein and a protective effect of the other. Interest in the effects of antihypertensive drugs on plasma lipoproteins was stimulated by the failure of these drugs in several clinical trials to reduce the incidence of coronary heart disease in hypertensive subjects, even though the incidence of other complications of high blood pressure were reduced. Many beta-blocking drugs and thiazides have now been shown to have a theoretically adverse effect on the plasma lipoprotein profile, measured in the terms of the ratio of HDL cholesterol to LDL. Although the consequences of these changes and their mechanisms remain to be established, they may explain the negative outcome of the prevention trials, the protection against coronary disease offered by the reduction of blood pressure being offset by the associated changes in lipoprotein metabolism.
Adult↗
Plasma apolipoprotein B metabolism in familial type III dysbetalipoproteinaemia.
Lipoprotein metabolism was studied in eleven patients with Type III hyperlipoproteinaemia, one with normolipidaemic dysbetalipoproteinaemia and eight controls. Apolipoprotein B kinetics in very low density, intermediate density and low density lipoproteins (VLDL, IDL and LDL) was investigated. Fractional catabolic rates (FCRs) of VLDL-apo B and IDL-apo B were lower (P less than 0.005 and P less than 0.001) in the patients: 0.064 +/- 0.018 and 0.059 +/- 0.006 h-1 respectively, (mean +/- SEM), compared with 0.219 +/- 0.035 and 0.243 +/- 0.028 h-1. Synthetic rates (SRs) of IDL-apo B varied widely from 1.5 mg kg-1 day-1 in the subject with normolipidaemic dysbetalipoproteinaemia to 2.8-25.2 mg kg-1 day-1 in Type III. The mean time for conversion of IDL-apo B to LDL-apo B was prolonged, 18.7 h compared with 3.8 h in the controls (P less than 0.001). LDL-apo B pool size and SR were lower in the patients (P less than 0.05 for both). Two patients treated with gemfibrozil showed reduced hyperlipidaemia and decreased SR of VLDL-apo B and IDL-apo B. Dysbetalipoproteinaemia is associated with pronounced impairment of IDL and VLDL-remnant catabolism, lipoprotein levels reflecting an interaction between this defect and SR of these lipoproteins.
Adult↗
Isozyme selectivity of the inhibition of rat liver cytochromes P-450 by chloramphenicol in vivo.
The isozyme-selectivity of chloramphenicol as an inhibitor of rat liver cytochromes P-450 has been investigated. Untreated rats and rats treated with the inducers phenobarbital, beta-naphthoflavone, pregnenolone 16 alpha-carbonitrile, and clofibrate have been injected intraperitoneally with chloramphenicol, and inhibition of specific cytochrome P-450 isozymes has been assessed by monitoring the metabolism of warfarin, testosterone, isosafrole, or lauric acid in subsequently prepared hepatic microsomal preparations. Of eight major cytochrome P-450 isozymes which could be monitored in this fashion, three were inhibited by more than 50% by a dose of chloramphenicol of 300 mg/kg, whereas no evidence of inhibition of the remaining isozymes was obtained. P-450PB-C, an isozyme which is present in significant amounts in untreated rats and which is induced approximately 2-fold by phenobarbital, was the most susceptible cytochrome P-450 to inhibition by chloramphenicol both in vivo and in vitro. P-450PB-B, the major phenobarbital-inducible isozyme, and P-450UT-A, a male-specific testosterone 2 alpha- and 16 alpha-hydroxylase, were intermediate in their susceptibility to chloramphenicol. In contrast, the major isozymes induced by beta-naphthoflavone, pregnenolone 16 alpha-carbonitrile, and clofibrate, as well as a constitutive testosterone 7 alpha-hydroxylase, were not inhibited by chloramphenicol.
Animals↗