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Biomedical subjects

A Dunn

Publications and source records attributed to A Dunn.

At least 127 records · Page 7Linked to original sources
PubMed1975

Effect of narcotic drugs on ribonucleic acid and nucleotide metabolism in mouse brain.

Mice either were administered 10, 30 or 100 mg/kg of morphine sulfate acutely or were chronically implanted with pellets containing morphine, naloxone or pentazocine. They were then injected intraperitoneally or intracerebroventricularly with [5-3H] uridine or [5-3H] orotic acid either 30 minutes, 24 hours of 48 hours before sacrifice. The incorporation of the 3H into brain total homogenate, ribonucleic acid (RNA) and uridine nucleotides was measured. The RNA content of brain and liver was also assayed. When [3H] uridine was injected. i.p. 30 minutes before sacrifice, acute injection of 30 or 100 mg/kg of morphine sulfate or chronic implantation of morphine pellets decreased the incorporation of the [3H] uridine into brain RNA. However, neither the acute administration of 10 mg/kg of morphine sulfate, nor the chronic administration of naloxone or pentazocine, altered the amount of radioactivity incorporated into RNA. Chronic morphine treatment decreased the incorporation of 3H into uridine nucleotides and nucleotide sugars due partially to increased catabolism of the [3H] uridine. The brain and liver RNA concentration was unchanged by chronic morphine administration. Thus, chronic morphine treatment alters the metabolism of uridine nucleotides but does not appear to alter the net synthesis of the total brain RNA.

Animals↗
PubMed1974

Enough to go round?

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Economics, Nursing↗
PubMed1974

Evaluation of glucose turnover, body mass and recycling with reversible and irreversible tracers.

1. Methods are presented for the calculation of rates of synthesis or loss, mean transit time and total body pool of compounds from specific-radioactivity curves, without assuming a multicompartmental model and without fitting the data by exponential expressions. The methods apply to the steady state after either single injection or continuous infusion of a labelled compound. 2. The use of irreversible and reversible tracers and the effects of recycling of carbon on the estimations of the parameters of glucose metabolism are discussed. Methods for quantitatively determining recycling of glucose carbon by the use of glucose doubly labelled with (14)C and (3)H are presented.

Carbon↗
PubMed1974

Determination of synthesis, recycling and body mass of glucose in rats and rabbits in vivo 3H-and 14C-labelled glucose.

1. Glucose labelled with (3)H in position 2 and uniformly with (14)C was administered simultaneously to rabbits and rats either as a single injection or by continuous infusion. Plasma glucose specific radioactivity and the yield of (3)H in the plasma water were monitored. 2. The rates of synthesis, recycling of carbon and total body mass of glucose were calculated, without assuming a multicompartmental model and without fitting data by exponential expressions. 3. The rate of synthesis of glucose in starved-overnight rabbits was 4mg/min per kg (range 3-4.5mg/min per kg) and 25-35% of the glucose carbon was recycled. The mass of total body glucose in starved rabbits was 290mg/kg (range 220-390mg/kg). About one-third of the total body glucose equilibrates nearly instantaneously with plasma glucose. 4. In rats starved overnight, glucose synthesis was about 10mg/min per kg and recycling of carbon ranged from 30-40%. Total body mass (per kg body weight) is similar to that in rabbits. 5. The activity in plasma water after injection of [2-(3)H]glucose was determined. The initial rate of (3)H(2)O formation is rapid, indicating that the major site of glucose catabolism is in the rapidly mixing pool. The curve of total body glucose radioactivity was obtained from the (3)H(2)O yield, and total mass of glucose was calculated. This agrees with that obtained from the (3)H specific-radioactivity curve.

Animals↗
PubMed1974

Chemical conversion of aspartic acid 52, a catalytic residue in hen egg-white lysozyme, to homoserine.

Hen egg-white lysozyme (EC 3.2.1.17) was specifically esterified at aspartic acid 52 by the affinity labeling reagent 2',3'-epoxypropyl beta-glycoside of di-(N-acetyl-D-glucosamine) [Eshdat et al. (1973) J. Biol. Chem.248, 5892]. The disulfide bonds of the affinity-labeled enzyme and the aspartic acid 52-ester bond were reduced with dithiothreitol and sodium borohydride, respectively, resulting in the removal of the affinity label. The reduced protein contained 0.9 mole of homoserine and 1 mole less of aspartic acid per mole of protein, as compared to the native enzyme. It was reoxidized by a mixture of reduced and oxidized glutathione to yield a modified protein that possessed one-tenth of the activity of native lysozyme (presumably due to a contamination by regenerated lysozyme formed as a result of hydrolysis of the aspartic acid 52-ester bond during the chemical treatment). The native enzyme, after reduction and reoxidation in the same manner, retained its amino-acid composition, full enzymatic activity, and fluorescence properties. The modified lysozyme, containing homoserine 52, showed the same fluorescence spectrum as the native enzyme. With both proteins, the fluorescence maximum shifted to the blue to a similar extent upon the addition of the saccharide inhibitors tri-(N-acetyl-D-glucosamine) and the cell-wall tetrasaccharide (GlcNAc-MurNAc)(2). The modified enzyme bound these two saccharides with nearly the same binding constants as those found for native lysozyme and for lysozyme that was reduced and reoxidized. Since the side chain of homoserine is similar in size to that of aspartic acid, it is concluded that the loss of enzymatic activity is the direct result of the chemical modification of the carboxyl side chain of aspartic acid 52, thus showing that this amino acid is essential for the catalytic action of the enzyme.

Amino Acid Sequence↗