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Biomedical subjects

R J Roberts

Publications and source records attributed to R J Roberts.

At least 271 records · Page 15Linked to original sources
PubMed1978

A specific endonuclease from Bacillus caldolyticus.

The purification and characterization of a new restriction endonuclease, BclI from the extreme thermophile Bacillus caldolyticus is reported. This enzyme recognizes the sequence : formula: (see text) and cleaves at the positions indicated by the arrows.

Bacillus↗
PubMed1978

Recognition sequence of restriction endonuclease KpnI from Klebsiella pneumoniae.

We have determined the recognition sequence of the restriction endonuclease KpnI, previously isolated from Klebsiella pneumoniae. The enzyme cleaves the twofold rotationally symmetric sequence (see book for formula) at the positions indicated by the arrows, producing 3' protruding cohesive ends, four nucleotides in length. The specific cleavage site was unambiguously deduced using both 3' and 5' end analyses of KpnI generated restriction fragments of simian-virus 40 (SV40) DNA (1 site), adenovirus-2 (Ad-2) DNA (8 sites), and a plasmid (pCRI) DNA (2 sites).

Avian Myeloblastosis Virus↗
PubMed1978

A computer assisted method for the determination of restriction enzyme recognifion sites.

A computer program has been developed which aids in the determination of restriction enzyme recognition sequences. This is achieved by cleaving DNAs of known sequence with a restriction endonuclease and comparing the fragmentation pattern with a computer-generated set of patterns. The feasibility of this approach has been tested using fragmentation patterns of 0X174 DNA produced by enzymes of both known and unknown specificity. Recognition sequences are predicted for two restriction endonucleases (BbvI and SfaNI) using this method. In addition, recognition sequences are predicted for two other new enzymes (PvuI and MstI) using another computer-assisted method.

Base Sequence↗
PubMed1978

Effects of hypoxemia upon aminoglycoside serum pharmacokinetics in animals.

Hypoxemia causes significant alterations in aminoglycoside serum pharmacokinetics in adult rats and newborn rabbits. The aminoglycoside serum clearances were diminished in hypoxemic animals. Comparisons of intravenous and intramuscular administration imply a delay in uptake of drug from intramuscular injection sites under hypoxemic conditions.

Amikacin↗
PubMed1978

Oxygen toxicity in neonatal and adult animals of various species.

Neonatal and adult animals of five species were exposed to 95+% O2. Survival time and changes in lung antioxidant enzyme activity (superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GP)) in response to hyperoxia were determined. Adult animals succumbed to O2 lung toxicity in 3--5 days. Neonatal rats, mice and rabbits showed minimal lung changes after 7 days of hyperoxic exposure and these same neonatal animals showed rapid and significant increases in lung antioxidant enzyme activities. In contrast, neonatal guinea pigs and hamsters had no lung antioxidant enzyme response to hyperoxia and these neonates died in 95+% O2 as readily as their respective parent animals. Results from an in vitro hyperoxic exposure system suggest that the lack of enzymic response of the guinea pig (and hamster) neonates to O2 challenge is due to an inherent pulmonary biochemical unresponsiveness rather than to a deficiency of a necessary "serum factor." The results of this species and age study support the important role of the lung antioxidant enzyme defense system in protection of the lung from O2-induced injury.

Animals↗
PubMed1978

Influence of increasing age on lethality induced by carbon monoxide or hypoxic hypoxia.

Mice ranging in age from 2 to 150 days of age were exposed to 2,000 ppm carbon monoxide (CO) or 7.5% O2. 2-day-old mice were more resistant than older animals to the lethal effects of both CO and hypoxic hypoxia. The oldest age group (150 days) were also found to be more resistant than young adult mice to the lethal effects of both CO and hypoxic hypoxia. The role of body temperature in the age-dependent susceptibility was studied by altering the environmental temperature. Neonatal mice remained resistant to the lethal effects of CO until the environmental temperature reached 35 degrees C at which time the death rate of neonatal mice equaled that of the adult mice in 30 degrees C environment.

Age Factors↗
PubMed1978

The role of endotoxin in protection of adult rats from oxygen-induced lung toxicity.

Adult rats show evidence of severe lung damage after 72h of continuous exposure to hyperoxia (96-98% O2). Treatment of adult rats with a solution of Plasmanate, inadvertently contaminated with endotoxin-producing organisms, or with purified endotoxin itself markedly altered the lung toxicity associated with hyperoxic exposure (survival in treated animals = 110/113 [97%] versus survival in untreated animals = 56/172 [33%]). After 72h of hyperoxic exposure, the endotoxin-treated rats demonstrated significant increases in lung superoxide dismutase, catalase, and glutathione peroxidase activity, a protectant enzyme response not seen in untreated adult rats. The basis for endotoxin's protective effect from hyperoxic lung damage is believed to be related to the stimulated increase in activity of the pulmonary antioxidant enzyme defense system. Some previously known actions of endotoxin are speculated to also serve a protective function by opposing some of the usual detrimental effects of high concentrations of O2 on the lung.

Animals↗
PubMed1978

Oxygen toxicity: comparison of lung biochemical responses in neonatal and adult rats.

Neonatal rats (4--7 days old) and adult rats (approximately 80 days old) were continuously exposed to either 96--98% oxygen or air. Examination of the lungs of neonatal rats, who survived 5 days of oxygen exposure with no evidence of respiratory distress, showed significant increases in the pulmonary superoxide dismutase (SOD) activity (peak value: 144% of air-exposed controls), glutathione peroxidase (GP) activity (126%), glutathione reductase (GR) activity (122%), reduced glutathione (GSH) level (176%), and glucose-6-phosphate dehydrogenase activity (151%). Adult rats, most of whom succumbed within 3 days of oxygen exposure, did not show any significant increase in the activities of pulmonary SOD, GP, GR, and the level of GSH as compared to the air-exposed adult animals. Glucose-6-phosphate dehydrogenase was significantly elevated in the 72-hr oxygen-exposed adult rats. It is concluded that increases in the lung complement of SOD, GR, GP, and GSH in the neonatal rat during oxygen challenge may provide the mechanism(s) for their increased tolerance to hyperoxia-induced lung injury as compared to the adults.

Aging↗
PubMed1977

Mapping of restriction sites in the attachment site region of bacteriophage lambda.

A find structure map of the EcoRI fragment containing the lambda attachment-site region has been constructed. 38 different restriction endonucleases have been employed and 170 sites located in this fragment. In addition, sites in adjacent regions have been determined for several enzymes. Complete cleavage maps of the entire lambda genome have been obtained for endonucleases BglII, BluI, KpnI, SacI, SacII, SalI and XbaI. The strategy employed for mapping included comparison of deletion and substitution mutants, analysis of mixed digests, and detailed analysis of subfragments.

Chromosome Mapping↗