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Biomedical subjects

R J Roberts

Publications and source records attributed to R J Roberts.

At least 253 records · Page 14Linked to original sources
PubMed1979

Nucleotide sequence analysis of the leader segments in a cloned copy of adenovirus 2 fiber mRNA.

Fiber mRNA of adenovirus 2 has been used as a template for RNA-dependent DNA polymerase. The resulting cDNA/RNA hybrids have been inserted at the Pst I site of the plasmid vector pBR322 after A:T tailing. One recombinant plasmid, pJAW 43, has been characterized in detail and shown to contain sequences from the main body of fiber mRNA, the three leaders common to most late adenoviral mRNAs and a fourth leader found in some species of fiber mRNA. The complete DNA sequence of the leader region has been determined and does not contain the initiation codon AUG, although this codon does occur immediately downstream from the junction between the fourth leader and the main body of the fiber mRNA. The first leader (map coordinate 16.6) is 41 nucleotides long, the second (from 19.6) is 71 nucleotides, the third (from 26.6) is 88 nucleotides and the fourth (from 78.5) is 181 nucleotides. The location of junctions between viral leaders and intervening sequences has been determined by reference, where possible, to sequences of the adenovirus 2 genome. Although the presence of short repeated sequences at the boundaries of intervening sequences and leaders makes it impossible to locate the splice point unambiguously, all of the leader-intervening sequence junctions can be arranged to stress a common feature--the presence of the dinucleotides GT and AG at the 5' and 3' ends, respectively, of the intervening sequences. This prototype sequence, which has also been recognized at or near the splice points in other eucaryotic systems, is possibly part of a larger unit which serves as a recognition site for specific excision-ligation events that ultimately lead to the production of mature mRNAs.

Adenoviruses, Human↗
PubMed1979

Unusual base sequence arrangement in phage phi 29 DNA.

Susceptibility of Bacillus subtilis phage phi 29 DNA to 34 different restriction endoculceases was determined. Three enzymes, BglI, XbaI and BstEII, were found to cleave phi 29 DNA only once at specific sites. The sites of these single cleavages have been mapped. Thirteen enzymes did not cut phi 29 DNA. phi 29 HindIII DNA fragments inserted into pBR313 plasmid and propagated in Escherichia coli, were resistant to these restriction endonucleases. This result suggests that the insusceptibility is due to the absence of the nucleotide sequences on phi 29 recognized by the enzymes, and not to the presence of modified nucleotides.

Bacillus subtilis↗
PubMed1979

Therapeutic problems arising from the use of the intravenous route for drug administration.

The kinetics of drug delivery were studied under conditions of varying iv flow rates and varying sites of drug administration into an iv system. The iv sites and rates were selected on the basis of questionnaire data obtained from nursing personnel. The rate of drug delivery from the iv system was dependent upon the iv flow rate and site of injection of the drug into the iv system. Under conditions of slow iv flow rates (3 ml/hour) there was the expected time delay required for the drug to begin to be infused but an unanticipated protracted time required for actual completion of the drug infusion. Calculation of theoretical drug blood levels based on the results of these iv studies revealed very different blood levels of drug at respective times, including different peak concentrations, depending on the iv flow rate and site at which the drug was injected into the system. Failure to appreciate the effects of slow iv rates and distal iv injection sites on actual rates of drug administration can adversely affect pharmacokinetic decisions and conceivably influence therapeutic success or failure.

Aminophylline↗
PubMed1979

Endotoxin protection against oxygen-induced acute and chronic lung injury.

Small dosages of endotoxin (100--500 micrograms/kg) provide significant protection against the acute manifestations of pulmonary O2 toxicity and lethality. Ninety-seven percent of endotoxin-treated adult rats survived a 72-h exposure to greater than or equal to 95% O2 with mimimal lung changes, compared to 32% of control animals (P less than 0.01). Exposure to greater than or equal to 95% O2 for 7 days resulted in a 20% survival rate in untreated control rats vs. 98% survival in endotoxin-treated rats (P LESS THan 0.01). Histological evaluation of lung from survivors revealed substantially less collagen and reticular fiber deposition in the endotoxin-treated animal lungs. Endotoxin treatment was associated with increased activity of the protectant antioxidant enzyme systems of the lung in an apparent dose-response manner. Endotoxin's protective activity against O2 toxicity does not appear to depend on an initial toxic insult to the lung like with alpha-naphthylthiourea, oleic acid, or alloxan treatment. The data support a protective role for endotoxin against the acute and the more chronic manifestations of O2-induced pulmonary injury.

Alloxan↗
PubMed1979

Effects of low-dose prenatal corticosteroid administration on the premature rat.

Administration of dexamethasone (0.2 mg/kg/day) to the pregnant rat on days 19 and 20 of gestation has been found to have marked effects on the body and organ weight of fetuses delivered 1 day prematurely on day 21 of gestation. Longer-term dexamethasone treatment earlier in gestation (days 14-18) had even more pronounced effects on body and organ weights in rat fetuses delivered three days prematurely. Dexamethasone treatment for 2 days prior to delivery had no effect on the survival of 1-, 2- and 3-day premature rats. The marked inhibitory effect on organ and body weight observed in the premature rats resulted from prenatal steroid therapy approximating that used in human pregnancies (dexamethasone 0.2 mg/kg/day for 48 h prior to premature delivery).

Animals↗