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G M Powell

Publications and source records attributed to G M Powell.

At least 37 records · Page 2Linked to original sources
PubMed1984

Molecular properties of radioiodinated apolipoprotein A-I.

Radioiodinated apolipoprotein A-I was separated into two pools by gel chromatography on Sephadex G-150 superfine resin or by high performance liquid chromatography using a TSK-2000 column. The first pool, pool 1, was indistinguishable from unlabeled apo-A-I as judged by sedimentation equilibrium, circular dichroic measurements, and radial immunodiffusion. This pool self-associated according to a monomer-dimer-tetramer-octamer scheme and underwent the expected conformation changes with dissociation as reported previously for unlabeled apo-A-I. The radioiodinated material in pool 2 had less secondary structure as compared to the unlabeled material and did not self-associate. Protein in this pool was immunochemically less reactive than unlabeled apo-A-I. Kinetic studies, in vivo, demonstrated that these two pools of radioiodinated apo-A-I are also distinguished metabolically. Discussion centers around possible mechanisms of formation of the incompetent protein in pool 2 and factors that should be taken into consideration when using unfractionated radioiodinated apo-A-I for experimental studies.

Adult↗
PubMed1984

Power spectral density analysis of lateral human standing sway.

A number of investigators have used power spectral density (PSD) analysis to try to identify and quantify various sensory systems which are involved in upright standing. Using PSD analysis, over a frequency range from 0.02-2.5 Hz, the present study examined two trials of lateral sway in each of 80 men. The results showed that little change occurred in PSD values between the first and second trials. Exponential curves were fit to the averaged trials data of each subject. The values of the parameter estimates obtained from the curve-fitting were regressed on the values of various direct, and derived anthropometric variables to try to explain the variance of the parameter estimates in terms of the anthropometrics. The subject's center of gravity location accounted for no more than 15.8% of the parameter variance, whereas the remaining anthropometrics explained even less. The overall averaged data suggest that three functions (related to visual, vestibular, and proprioceptive processes) may underlie the sway pattern over this frequency range. PSD curves of individuals with a history of high-level athletic activity clearly differed from those of sedentary subjects.

Journal Article↗
PubMed1984

Intestinal transport of 5-methyltetrahydrofolate.

The mechanism of intestinal absorption of 5-methyltetrahydrofolate (5- CH3THF ) has been the topic of some controversy. In the present study, we have used enzymatically prepared 5- CH3THF to characterize transport by rat intestinal loops in vivo and everted jejunal sacs in vitro. Transport of 5- CH3THF is saturable (Km = 5.2 microM) and highly pH dependent, with the rate of maximal transport occurring at pH 5.8. Transport is competitively inhibited by folic acid (Ki = 4.2 microM) and methotrexate (Ki = 4.65 microM). Metabolic poisons and anaerobiosis greatly reduce 5- CH3THF transport. We conclude that 5- CH3THF transport in the rat intestine occurs by the same structure-specific mechanism responsible for the transport of unreduced folic acid and other monoglutamyl folates.

Animals↗
PubMed1983

The effect of sensory irritants on phagocytosis by pulmonary macrophages.

The phagocytosis of Staphylococcus epidermis by rabbit alveolar macrophages was measured in the absence or presence of a series of sensory irritants. The phagocytic index was determined in the presence of the sensory irritant dibenzoxazepine and 10 of its derivatives. All of the compounds tested inhibited phagocytosis to some extent. Dibenzoxazepine was the most potent inhibitor and the 1-chloro and 2-chloro derivatives were the least potent. With all the compounds tested, the inhibition of phagocytosis was dose dependent. The degree of inhibition of phagocytosis was not correlated with either the nature or the position of the substituent groups on the dibenzoxazepine molecule. There was no discernible relationship between the inhibition of phagocytosis and the irritancy of the compounds tested.

Animals↗
PubMed1983

The fate of dibenz[b,f]-1,4-oxazepine (CR) in the rat, rhesus monkey and guinea-pig. Part I. Metabolism in vivo.

The fate of dibenz[b,f]-1,4-[11(14)-C]oxazepine (CR) in rats, rhesus monkey and guinea-pig and in isolated perfused rat livers has been examined. 14C-CR was administered to rats at doses from 1.56 to 3470 mumol/kg and irrespective of dose or route of administration most (59-93%) was eliminated in the urine as primarily the sulphates of the 7-, 4- and 9-hydroxylated 10,11-dihydrodibenz[b,f]-1,4-oxazepine-11(10H)-one. In blood, both in vivo and in liver perfusates, CR concentrations decreased biphasically to be replaced initially with CR-lactam (dihydrodibenz[b,f]-1,4-oxazepine-11(10H)-one), followed by the sulphates of the 7-, 4- and 9-hydroxylactams. The rate of disappearance of CR in liver perfusates was slower than in vivo. Bile contained only small amounts of sulphate conjugates and significant amounts of conjugated 2-amino-2'-hydroxymethyldiphenyl ether (amino alcohol). This was not identified in the urine or blood of rats. Preliminary studies in rhesus monkey and the guinea-pig show similar excretory patterns and metabolites. However, only free hydroxylactams were isolated from monkey urine and traces of the amino alcohol were detected in guinea-pig urine. Whole-body autoradiography of mice confirm the rapid disappearance of CR from blood into heart, liver, kidneys and small intestine with evidence of biliary excretion. It is consistent with the rat studies showing the rapid absorption of a highly lipophilic compound undergoing hepatic metabolism, biliary secretion, enterohepatic recirculation and renal excretion.

Animals↗
PubMed1983

The fate of dibenz[b,f]-1,4-oxazepine (CR) in the rat. Part III. The intermediary metabolites.

The fates of several intermediates of dibenz[b,f]-1,4-oxazepine (CR) metabolism in vivo and in vitro in rats have been examined to establish the metabolism and excretory sequence of CR. The ring-opened 2-amino 2'-hydroxymethyldiphenyl ether (amino alcohol) added to isolated perfused rat liver was rapidly cleared in bile as a mixture of highly polar conjugates, whereas the major route of excretion in vivo was as the 4-, 7- and 9-hydroxylactam sulphates in urine. The lactam of CR was eliminated exclusively in urine giving the same products as obtained for CR, but the distribution of metabolites of the C10-C11 dihydro derivative of CR was unlike that of the parent compound indicating that it occupies only a peripheral role in the fate of CR in vivo. A mixture of 7-, 4- and 9-hydroxylactams derived from the enzymic hydrolysis of urinary sulphates was rapidly removed from blood, sulphated and secreted as sulphates into blood both in vivo and in isolated perfused liver. Little biliary excretion occurred. When the urinary sulphates of the hydroxy lactams were administered i.v. to rats, 70% was eliminated in urine within 1 h; however, if the kidneys were ligated biliary excretion of sulphate was higher (58% in 5 h). After intraduodenal administration of the biliary conjugates of CR metabolism, all of the dose was resorbed to be re-secreted in bile or excreted as sulphates in urine. These studies confirm that the major metabolic fate of CR in the rat is oxidation to lactam, followed by ring hydroxylation, sulphation and urinary excretion.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1983

The fate of fenclozic acid in the gut and its effect on some aspects of gut metabolism.

In the rat [14C]fenclozic acid is not metabolized in the gut and passes into the portal blood unchanged. After intraduodenal administration of [14C]fenclozic acid, a small proportion of the dose binds to high molecular weight substances in the gut wall. The incorporation of L-[U-14C]leucine and N-[3H]acetyl-D-glucosamine into acid-precipitable materials by isolated mucosal cells and homogenates of gut mucosal cells was inhibited by fenclozic acid in a dose-dependent manner. Other non-steroidal anti-inflammatory drugs (indomethacin, phenylbutazone, prednisolone, salicylic acid and paracetamol) were tested for their potency as inhibitors of glycoprotein production by whole cell preparations and by homogenized gut cell preparations. Marked differences were observed in the inhibitory potency of indomethacin, paracetamol and salicylic acid in the two experimental systems. Fenclozic acid had no major effect on the rate of total glycoprotein production by the isolated perfused rat liver or by the duodenal mucosa in situ. Fenclozic acid displaces albumin-bound [3H]tryptophan and increases the level of hepatic tryptophan pyrrolase approx. threefold. The inhibition of gut glycoprotein production by fenclozic acid was not prevented by free tryptophan.

Amino Acids↗
PubMed1982

Response to live attenuated measles vaccine in children with severe kwashiorkor.

An impaired response to vaccination with live attenuated measles vaccine was found in severely malnourished children, when compared with well nourished controls. It is suggested that humoral immune response may fail in children with severe protein energy malnutrition due to diversion of available amino acids to other uses. The possibility of a delayed antibody response to measles vaccine in malnourished children was not excluded.

Antibodies, Viral↗
PubMed1982

The effect of configuration of the sulphate moiety on the metabolism of potassium octan-2-sulphate in the rat.

1. A comparison was made of the metabolism of potassium D-(+)-octan 2-[35S]sulphate and potassium L-(-)-octan-2-[35S]sulphate in the rat. 2. Following administration of either enantiomer orally or i.v. the major proportion of the radioactivity was excreted in the urine within 24 h. When either enantiomer was administered i.v. to rats with bile-duct and ureter cannulae, the majority of the radioactivity was eliminated in the urine within six hours with only small amounts in bile. 3. Both enantiomers were extensively degraded in vivo. The metabolic products were identical with those previously reported (Maggs et al. 1982). 4. The major difference in the metabolite patterns was with respect to the relative amounts of hexanoate-5-sulphate: male and female urines contained approx. twice as much of this metabolite when the D-(+)-isomer was administered. In addition, isomer and sex-linked differences were observed with respect to the amounts of octanoate-7-sulphate.

Animals↗
PubMed1982

Metabolism in the rat of potassium DL-octan-2-sulphate, a secondary alkyl sulphate.

1. The metabolism of potassium [2-14C]octan-2-sulphate and potassium octan-2-[35S]sulphate was investigated in the rat. Following oral administration, the bulk of the radioactivity was eliminated in the urine within 24 h. 2. Whole-body radioautography showed the liver to be the principal site of tissue accumulation of radiolabel following administration of 14C- or 35S-labelled DL-octan-2-sulphate. 3. Octan-2-sulphate was extensively degraded in vivo. The major urinary components are five sulphate estes, present in urine in essentially the same proportions regardless of label. The relative proportions of radioactivity associated with the urinary components showed considerable differences between male and female rats. 4. Three of the components have been identified as butanoate-3-sulphate, hexanoate-5-sulphate and octanoate-7-sulphate. The remaining metabolite was tentatively identified as an aldehyde derivative of octan-2-sulphate, a possible intermediate in the formation of octanoate-7-sulphate.

Animals↗
PubMed1981

The enhanced biliary secretion of a taurine conjugate in the rat after intraduodenal administration of high doses of fenclozic acid.

1. The metabolic fate of [14C]fenclozic acid (ICI 54450) in rat was determined after intraduodenal administration at different doses. 2. Increasing the dose from 2 to 100 mg/kg resulted in a five-fold increase in drug-related material secreted in bile. 3. At a dose of 2 mg/kg the taurine conjugate was a relatively minor metabolite, whereas at 100 mg/kg this conjugate was the major metabolite in bile and urine. 4. Enhanced biliary secretion of the taurine conjugate in rats receiving multiple doses of fenclozic acid results in exposure of the intestinal cells to much greater concn. of drug-related metabolites.

Animals↗
PubMed1980

Analysis of the mixed association between human apolipoproteins A-I and A-II in aqueous solution.

The mixed association between two self-associating systems, human apolipoproteins A-I and A-II, has been evaluated by fluorescence spectroscopy and sedimentation equilibrium. The combined results are consistent with the formation of specific mixed oligomers between apolipoproteins A-I and A-II in aqueous solution. The data are discussed in terms of the role of protein-protein versus protein-lipid interactions in the quaternary organization of plasma lipoproteins.

Apolipoprotein A-I↗
PubMed1980

Kinetic measurements of the biliary excretion of metabolized compounds.

1. Rats received constant infusions of bromosulphophthalein or [carboxy-14C]cholic acid at a range of concentrations. 2. Kinetic parameters describing the biliary excretion of the compounds were determined. 3. The biliary excretion of both compounds could be described by the same kinetic parameters already calculated for phenolphthalein disulphate, which is excreted in the bile unchanged.

Animals↗