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Biomedical subjects

R J Roberts

Publications and source records attributed to R J Roberts.

At least 307 records · Page 17Linked to original sources
PubMed1976

Acetaminophen elimination kinetics in neonates, children, and adults.

The elimination of acetaminophen (APAP) following an oral dose of 10 mg/kg in newborn infants, children, and adults was compared. Urinary excretion of unchanged APAP, APAP-sulfate, and APAP-glucuronide was complete within 30 hr at all ages. Higher percentages of the dose were excreted in the urine as APAP-sulfate in neonates (0-2 days old) and children (3-9 yr old) than in 12-yr old children and adults. A pharmacokinetic analysis indicated that the higher rate of APAP-sulfate formation in younger age groups apparently compensated for a deficiency in glucuronide formation. No dramatic age-related differences in the overall elimination rate constant for APAP were observed despite the quantitative changes in the metabolic pathways during early childhood.

Acetaminophen↗
PubMed1976

Modification of alveolar hyperoxia induced pulmonary vasodilatation by indomethacin.

Decrease in pulmonary vascular resistance was observed in neonatal minature pigs breathing 100% O2 or 95% O2:5% CO2. The pulmonary vasodilator response to hyperoxia ventilation was reduced by indomethacin in the intact animal and in the isolated perfused lung preparation. In the isolated perfused lung preparation, it was also shown that lung alveolar pO2 rather than pulmonary arterial pO2 was responsible for the pulmonary vasodilation. The study suggests that alveolar hyperoxia induced decrease in pulmonary vascular resistance may be mediated in part by release of prostaglandins. The relevance of this study with oxygen therapy in newborn infants is also discussed.

Animals↗
PubMed1976

Developmental characteristics of pulmonary superoxide dismutase: relationship to idiopathic respiratory distress syndrome.

Pulmonary superoxide dismutase (SOD) acitivity was determined for various groups of human fetuses, infants, and adults. Enzyme activity was found to increase with age from a low of 17 +/- 1 units/mg DNA in fetal lung to 49 +/- 6 units/mg DNA in infant lung and finally to 110.2 +/- 14.8 units/mg DNA in adult lung (P less than 0.05). No difference in lung SOD activity was demonstrated between normal infants and those with idiopathic respiratory distress/hyaline membrane disease (IRDS/HMD). No significant differences in SOD activity were found among all the samples of infant blood. Adult blood samples, however, contained significantly greater SOD activity both in terms of heme concentration and volume of whole blood (P less than 0.05). SOD activity in lung tissue from both rats and rabbits were also found to increase with age from a low value in fetal animals to a maximum activity in adults (P less than 0.05). Exposure of New Zealand White rabbits, prematurely delivered by caesarian section, to 80% oxygen for 24 hr resulted in a 42% increase in lung SOD activity. Similarly, 7-day-old Sprague-Dawley rats exposed to 85% oxygen for 24 hr showed a 43% increase in pulmonary SOD activity. No increase in pulmonary SOD was observed when adult rats were exposed to 85% oxygen for 24 hr. The effect of hyperoxia on SOD activity in excised lung was investigated. Rat lung, incubated in either heparinized whole blood or in plasma and exposed to 100% oxygen, showed a 30% increase in SOD activity after 2 hr. This capacity of lung tissue to respond to hyperoxia in vitro with increased SOD activity was age dependent. The maximum increase in SOD activity was seen with lungs from 10-12-day-old rats. The oxygen-stimulated increase in lung SOD activity disappeared at about 19-20 days of age.

Adult↗
PubMed1976

Restriction endonucleases.

This review provides a comprehensive account of the current status of the biology and biochemistry of restriction endonucleases. Both Class I and Class II restriction endonucleases will be considered. However, emphasis will be placed on the Class II group, which recognizes and cleaves a specific duplex DNA sequence. Their occurrence, purification, and characterization is discussed in detail. The characterization includes physical mapping information and determination of recognition sequences. In addition to detailed discussions of the biochemical properties of the enzymes, considerable attention is paid to the uses of these enzymes as tools for research in molecular biology. These uses include physical mapping of genomes and their transcripts, genetic analysis (marker rescue, etc.), DNA sequence analysis, analysis of complex genomes, and genetic engineering. Specific examples of each use are outlined. Practical aspects of both the isolation and use of the restriction endonucleases form the major theme of this review.

Bacteria↗
PubMed1976

Comparison of sulfobromophthalein (BSP) and sulfobromophthalein glutathione (BSP-GSH) disposition under conditions of altered liver function and in the isolated perfused rat liver.

Disposition of sulfobromophthalein (BSP) and sulfobromophthalein glutathione (BSP-GSH) was compared in control, phenobarbital, or alpha-naphthylisothiocyanate-(ANIT)-treated rats, and in the isolated perfused rat liver preparation. After dye administration, BSP-GSH was found to have a more rapid early plasma disappearance rate, a more rapid appearance in the liver, and a greater rate of biliary excretion both in vivo and in the isolated perfused liver, than that of BSP. In considering these observations, it is concluded that hepatic uptake as well as biliary excretion of BSP-GSH is faster than that of BSP. Comparing BSP and phenobarbital, augmentation or reduction in plasma dye concentration, mean plasma half-life (2 to 30 minutes), hepatic dye content, and bile dye concentration, were of the same order of magnitude for both dyes. However, with dye infusion of 3.6 mumoles per kilogram per minute, phenobarbital significantly enhanced the rate of biliary excretion of BSP but not BSP-GSH and ANIT treatment had a greater inhibitory effect on biliary excretion of BSP-GSH than BSP.

1-Naphthylisothiocyanate↗