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Biomedical subjects

R J Roberts

Publications and source records attributed to R J Roberts.

At least 217 records · Page 12Linked to original sources
PubMed1983

Lipid peroxidation in the newborn rat: influence of fasting and hyperoxia on ethane and pentane in expired air.

The rate of lipid peroxidation, as determined by expired air pentane and ethane measurements, was assessed in suckled or fasted newborn rats exposed to air or hyperoxia (FIO2 greater than 0.95). Pentane and ethane production in suckled newborn rats did not significantly change with exposure to hyperoxia after birth. Pentane production averaged over a 3-day exposure period was 2.8 pmol/100 g/min in hyperoxia versus 2.5 pmol/100 g/min in air. However, significant increases in ethane production occurred in fasted newborn rats over the first 18 h of life (less than 2.5 pmol/100 g/min increasing to greater than 6 pmol/100 g/min), which were not observed in suckled animals. Although hyperoxia did not cause an increase in pentane or ethane production above air-exposed controls, nutritional deprivation in newborn rats appeared to accelerate lipid peroxidation events and resulted in high mortality in newborn rats exposed to hyperoxia.

Animals↗
PubMed1983

Postnatal increase in airway surfactant in the premature rabbit exposed in utero to betamethasone.

In utero exposure to betamethasone on days 26 and 27 of gestation resulted in a significant increase in lung lavage phospholipid after 24 h of air breathing in rabbit pups delivered at 29 days of gestation. At 6 h of age, the proportion of type II epithelial cells in betamethasone-exposed newborns was nearly twice the saline-exposed control value. Phospholipid composition and pressure:volume analysis of compliance were both unaffected by betamethasone treatment. The betamethasone-associated increase in airway phospholipid content was observed only in female pups. These data support the conclusion that antenatal betamethasone treatment elicits an increase in airway phospholipid which is dependent on breathing and confined to the female newborn.

Animals↗
PubMed1983

Oxygen-induced alterations in lung vascular development in the newborn rat.

Newborn rats were exposed to air or hyperoxic conditions for the first 6 days of life. Resulting effects on the pulmonary vascular bed were determined by analysis of barium angiograms, scanning electron microscopy of methylmethacrylate corrosion casts and whole lung, morphometric estimations of pulmonary arteries/area and capillary number/area, and arterial blood gas measurements. Similar studies were also performed on the lungs of animals allowed to recover in air for 1 and 2 wk. Although the general pattern of the pulmonary arterial bed by barium angiograms appeared similar, diminished branching or underfilling of the distal arterial segments was more frequently encountered in hyperoxic-exposed animals. Morphometric examination and corrosion casts revealed differences in vascular pattern and density between hyperoxia and air-exposed animals. The number of capillaries/mm2 of lung tissue was less in hyperoxic-exposed pups than controls after 6 days of exposure to hyperoxia but markedly increased to slightly above control levels by 2 wk of air recovery. The number of 20--50 micrometers size vessels/mm2 followed a similar pattern of change. Corrosion casts of lung exposed to 6 days of hyperoxia revealed less microvascular density compared to air controls, but after 1 wk recovery in air, hyperoxic-exposed animal had a more extensive network of microvessels. Maximum PaO2 attained by animals in the various groups closely resembled the patterns of change in microvessel density. These findings support the thesis that a major alteration of lung vascular growth and development occurs subsequent to exposure of the newborn to hyperoxia.

Animals↗
PubMed1982

Nucleotide sequences from the adenovirus-2 genome.

The sequence of 15,441 nucleotides from the adenovirus-2 genome has been determined and includes the regions between coordinates 0-32% and 89-100%. These regions contain the early (E) transcription units E1A, E1B, E2B, and E4, the genes for polypeptides IVa2 and IX, the COOH terminus of fiber polypeptide, as well as the two virus-associated RNAs and the leader sequences for the major late mRNAs. Analysis of tryptic peptides from the terminal protein and its precursor (Smart, J. E., and Stillman, B. W. (1982) J. Biol. Chem. 257, 13499-13506) has allowed the gene for the precursor terminal protein to be positioned between coordinates 28.0 and 23.5 on the 1-strand. A minimum Mr = 74,500 is predicted. A second, longer open reading frame is also found on the 1-strand between coordinates 22.9 and 14.2 and predicts a polypeptide of at least Mr = 120,000. Many open reading frames longer than 10,000 exist within this sequence although less than half of them can be assigned to previously characterized polypeptides. As with other viral genomes, the available coding information is highly compressed. Intergenic distances are very short and examples are found of genes which overlap either on the same strand or the complementary strand.

Adenoviruses, Human↗
PubMed1982

Modification profiles of bacterial genomes.

DNAs were prepared from twenty-six bacterial species and digested with a variety of restriction endonucleases to determine what modifications the DNAs carry. Several general conclusions could be made: 1) First, in no instance was the DNA of a restriction enzyme. 2) The specificity of the DNA modification was the same as that of its restriction counterpart; there were no cases of the DNAs being modified against a less specific class of restriction enzymes. 3) In most (but not all) cases, the resistance of a bacterium's DNA to its own restriction enzyme could be generalized to include resistance to all other restriction enzymes with the same specificity (isoschizomers). 4) DNA modified within the central tetramer of a recognition sequence is usually protected against cleavage by all related hexameric enzymes possessing that central tetramer. Only three families of DNA presented in this study disobey this rule. 5) Finally, a significant number of cases emerge where bacterial DNA carries a modification but no corresponding restriction endonuclease activity.

Bacteria↗
PubMed1982

A semi-automated method for the reading of nucleic acid sequencing gels.

A collection of computer programs is described which permit automatic entering of nucleotide sequence data directly from an autoradiograph into a computer. This collection, called DIGITPAD, makes use of a digitizing tablet for the data entry and allows the rapid and accurate transfer of the sequence into the computer.

Base Sequence↗
PubMed1982

Preface.

Explore the source record for details and available documents.

Journal Article↗
PubMed1982

Optimal lidocaine dosing in patients with myocardial infarction.

A decrease in hepatic clearance and volume of distribution in patients with congestive heart failure frequently leads to toxicity when drugs such as lidocaine are administered. To determine the effect of adjusted dosing of lidocaine in patients with myocardial infarction, we studied 32 patients receiving lidocaine either by a conventional method (control group: 1-2 mg/kg bolus, then 1 to 4 mg/min) or by an adjusted regimen based on the presence or absence of heart failure [experimental group: 1-2 mg/kg bolus; then, class I (no heart failure), 35 to 88 micrograms/kg/min; class II (heart failure), 12 to 35 micrograms/kg/min]. Plasma lidocaine levels were determined at 2 and 5 h of the infusion by enzyme multiplied immunoassay technique (EMIT) and gas liquid chromatography (GLC). Ten of 33 determinations in the control group were in the toxic range, i.e., greater than 6 micrograms/ml, and four others were subtherapeutic, i.e., less than 2 micrograms/ml. In contrast, 13 of 16 determinations in the experimental group were in the therapeutic range, and none were in the toxic range. These data show that administration of lidocaine by a conventional method may produce diverse plasma levels that may occasionally be in the toxic range. Modified dosing based on cardiac status may result in optimal levels in most patients.

Adult↗
PubMed1982

Resident enhanced repair: novel repair process action on plasmid DNA transformed into Escherichia coli K-12.

The survival of UV-irradiated DNA of plasmid NTP16 was monitored after its transformation into recipient cells containing an essentially homologous undamaged plasmid, pLV9. The presence of pLV9 resulted in a substantial increase in the fraction of damaged NTP16 molecules which survived in the recipient cells. This enhanced survival requires the host uvrA+ and uvrB+ gene products, but not the host recA+ gene product. The requirement for both homologous DNA and the uvrA+ and uvrB+ gene products suggests that a novel repair process may act on plasmid DNA. Possible mechanisms for this process are considered.

DNA Repair↗
PubMed1982

A comparison of various types of patient instruction in the proper administration of metered inhalers.

The administration technique employed by 42 inpatients using metered inhalers were observed. Proper performance of the six steps recommended by the manufacturer provided the guidelines for correct administration. The degree of compliance with proper technique was defined as the number of steps correctly executed by the patient. The mean number of steps correctly performed was 2.9 out of the possible six (48.3 percent). Twenty-four patients were then randomized into one of three groups. Group I received the manufacturer's instruction sheet, Group 2 received counseling from a pharmacist, and Group 3 received both the manufacturer's instruction sheet and counseling from a pharmacist. There was a significant improvement in the postinstruction technique in Groups 2 and 3, while Groups 1 failed to demonstrate any significant improvement. Comparisons were then made among the three groups. No significant difference was found between Group 2 and Group 3. However, both Groups 2 and 3 were found to be significantly different (p less than 0.05) from Group 1. This study shows that pharmacist counseling can significantly improve the degree of patient compliance in the administration of metered inhalers.

Aerosols↗
PubMed1982

Pulmonary superoxide dismutase activity in the euthyroid and hypothyroid ovine fetus.

Pulmonary superoxide dismutase (SOD) activity was measured in 11 euthyroid and 15 hypothyroid ovine fetuses at 130 days gestation. In the euthyroid fetus, the mean pulmonary SOD activity was similar in saline- and thyroxine-infused groups. Compared to the euthyroid fetus, the mean pulmonary SOD activity was significantly lower in the noninfused or saline-infused athyrotic fetus. Administration of thyroxine to the hypothyroid fetus results in a normalization of pulmonary SOD activity to control values. Thus, thyroxine appears to influence the maturation of pulmonary SOD activity in the ovine fetus during the third trimester.

Animals↗
PubMed1982

Effect of intravenous fluid and drug solution coadministration on final-infusate osmolality, specific gravity, and pH.

The effects of i.v. fluid rates and i.v. drug delivery rates on osmolality, specific gravity, and pH of the resulting infusate were examined. Selected drug solutions of various osmolalities and 5% dextrose and 0.2% sodium chloride injection or Ringer's injection, lactated, were administered simultaneously using a drug delivery system capable of controlling the flow rates independently. The i.v. fluid and drug infusion rates were varied from 4 to 46 and from 2 to 31 ml/hr, respectively. Osmolality, pH, and specific gravity of the drug solutions and final infusate were measured. Using alligation, the osmolality, pH, and specific gravity of the final infusate were calculated; correlations between observed and calculated values were computed. Guidelines for achieving an osmolality of the final infusate less than 500 mOsm/kg water were calculated. The observed and calculated osmolality and specific gravity of the final infusate were significantly correlated (r = 0.91, p less than 0.001, and r = 0.99, p less than 0.01, respectively). The pH of the final infusate was dependent on the pH of the original drug solution and was not affected by i.v. fluid and drug delivery flow rates. Osmolality may be an important factor to consider when establishing ideal drug solution infusion rates or concentrations. The infusate osmolality can be controlled by adjusting the concentration of the drug solution, drug infusion rate, or the i.v. fluid flow rate.

Hydrogen-Ion Concentration↗
PubMed1982

Effects of alpha-tocopherol treatment on newborn rat lung development and injury in hyperoxia.

The efficacy of alpha-tocopherol treatment to influence the pattern or extent of lung injury resulting during exposure of newborn rats to hyperoxia was assessed following six-day exposures to FIO2 0.21, 0.4, and greater than 0.95. Alpha-Tocopherol treatment was found incapable of preventing the developmental arrest of the lung that occurs during hyperoxic exposure, shown by assessments of wet lung weights, lung DNA, lung volumes, and the progress of secondary septal and capillary development. However alpha-tocopherol treatment was found effective in preventing the hyperoxic-induced lessening of lung compliance and in preventing the deterioration of gas exchange capacity in the lung of the hyperoxic-exposed newborn rat. These findings suggest alpha-tocopherol treatment may not be capable of preventing major alterations in lung morphology in infants with chronic lung disease may be lessened by preserving gas exchange capabilities.

Animals↗
PubMed1981

Two new restriction endonucleases from Proteus vulgaris.

Two novel sequence-specific endonucleases have been isolated from Proteus vulgaris, ATCC 13315. PvuI recognizes the sequence: 5' C G A T decrease C G 3' 3' G C increase T A G C 5' and PvuII recognizes the sequence: 5' C A G decrease C T G 3' 3' G T C increase G A C 5' and cleave as indicated by the arrow (decrease). PvuI is an isoschizomer of XorII, RshI, and XniI. No enzyme with the specificity of PvuII has been described previously.

Animals↗