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Biomedical subjects

H R Warner

Publications and source records attributed to H R Warner.

At least 91 records · Page 5Linked to original sources
PubMed1977

Properties of deoxynucleoside 5'-monophosphatase induced by bacteriophage T5 after infection of Escherichia coli.

Bacteriophage T5 induced a deoxynucleoside 5'-monophosphatase during its infection of Escherichia coli. The enzyme was purified about 100-fold. It was clearly distinct from the host 5'-nucleotidase activity in its physical characteristics and substrate specificity. The enzyme was active on deoxynucleoside 5'-monophosphates but was not active as a phosphatase on ribonucleotides, deoxynucleoside 5'-triphosphates, deoxynucleoside 3'-monophosphates, or deoxyoligonucleotides. Furthermore, it did not have oligonucleotidase or exonuclease activity. The enzyme could exist in multimeric form but had a monomer molecular weight of about 25,000.

Coliphages↗
PubMed1977

Isolation and characterization of a bacteriophage T5 mutant deficient in deoxynucleoside 5'-monophosphatase activity.

A bacteriophage T5 mutant has been isolated that is completely deficient in the induction of deoxynucleoside 5'-monophosphatase activity during infection of Escherichia coli F. The mutant bacteriophage has been shown to be deficient in the excretion of the final products of DNA degradation during infection of E. coli F, and about 30% of the host DNA's thymine residues were reinocorporated into phage DNA. During infection with this mutant, host DNA degradation to trichloroacetic acid-soluble products was normal, host DNA synthesis was shut off normally, and second-step transfer was not delayed. However, induction of early phage enzymes and production of DNA and phage were delayed by 5 to 15 min but eventually reached normal levels. The mutant's phenotype strongly suggests that the enzyme's role is to act at the final stage in the T5-induced system of host DNA degradation by hydrolyzing deoxynucleoside 5'-monophosphates to deoxynucleosides and free phosphate; failure to do this may delay expression of the second-step-transfer DNA.

Coliphages↗
PubMed1976

Early events after infection of Escherichia coli by bacteriophage T5. II. Control of the bacteriophage-induced 5'-nucleotidase activity.

The control of activity of the bacteriophage T5-induced 5'-nucleotidase is dependent upon the amount of T5 parental DNA injected into the cell and expressed. When only the first-step transfer DNA is injected and expressed the amount of 5'-nucleotidase activity observed is two to three times the maximum amount observed after normal T5 infection, and inactivation of the enzyme does not occur. Enzyme inactivation occurs only after the remaining DNA is injected, but only limited expression of this DNA is required. The control of the nucleotidase inactivation process is similar to that for the repair of the nicks in parental DNA, and is probably mediated by a class IIa protein.

Calcium↗
PubMed1976

Computerized medication monitoring system.

A computerized medication monitoring system for alerting and warning of potential adverse drug reactions is described. The system integrates computerized data on each hospital patient (medications, clinical laboratory, blood gas, ECG, ALLERGIES, DIAGNOSIs, etc.) and returns to the pharmacist warning messages and suggestions regarding patient drug therapy. The broad data base allows for nearly complete drug therapy monitoring. When a warning message is received, the pharmacist contacts the physician or nursing staff and explains the potential problem. The system also generates prescription labels and patient drug profiles which are used in a unit dose dispensing system. Five percent of 13,727 patients monitored have had drug alerts. Of these alterts, 44.9% were drug-laboratory contraindications and only 28.9% were drug-drug interactions. Of the 690 alerts received, 77% resulted in the physician changing the patient's therapy.

Computers↗
PubMed1975

Isolation of an Escherichia coli mutant deficient in glutathione synthesis.

A mutant of Escherichia coli that contains essentially no detectable glutathione has been isolated. The mutant contains a very low level of the enzyme glutathione synthetase and accumulates lambda-glutamyl cysteine at a concentration approximately equal to the level of glutathione found in its parent. No significant differences in growth were observed between the mutant and its parent. However, the activity of at least one enzyme was found to be affected by the absence of glutathione; the specific activity of the B1 subunit of ribonucleoside diphosphate reductase was greatly reduced. The possibility that the decreased B1 activity is due to a mutation in the structural gene coding for B1 or its regulatory gene could be eliminated. This suggests that one role of glutathione in the cell is to maintain at least this one protein in an active state. We propose the designation gshB for the gene coding for glutathione synthetase.

Cell-Free System↗
PubMed1975

Early events after infection of Escherichia coli by bacteriophage T5. Induction of a 5'-nucleotidase activity and excretion of free bases.

Thymine-containing compounds, produced degradation of Escherichia coli DNA after infection of the cells with bacteriophage T5, did not accumulate in the cell but were excreted into the medium as the DNA was degraded. The ultimate degradation product was extracellular thymine that was not reutilized when T5 DNA synthesis began. This excretion of thymine may have been due in part to the induction of 5'-nucleotidase activity within 3 min after T5 infection. The level of this activity reached a maximum between 4 to 6 min after infection and then rapidly declined to its preinfection level by 10 to 15 min after infection. Chloramphenicol added before or soon after infection prevented the appearance of the nucleotidase. The induced nucleotidase activity was active not only on dTMP but also on dAMP, dGMP, and dCMP.

Carbon Radioisotopes↗
PubMed1975

Identification of P48 and P54 as components of bacteriophage T4 baseplates.

The involvement of two bacteriophage T4 gene products in the initiation of T4 tail tube and sheath polymerization on mature baseplates has been studied by radioautography of acrylamide gels of various partially completed tail structures. The products of genes 48 and 54 (P48[the nomenclature P48 refers to the protein product of bacteriophage T4 gene 48] and P54), which are known to be required for the synthesis of mature baseplates, have been shown to be structural components of the baseplate. These gene products have molecular weights of 42,000 and 33,000, respectively. The addition of P54 to the baseplate not only permits the polymerization of the core protein, P19, onto the baseplate, but also caused the disappearance of a polypeptide of molecular weight about 15,000 from the supernatant fraction of infected cells. Another gene product, P27, has been identified in the crude extracts of infected cells. This gene product, which is required for the synthesis of baseplate structures, has the same mobility as one of the unidentified structural polypeptides of the baseplate and is therefore probably also a baseplate component.

Coliphages↗
PubMed1974

Isolation and partial characterization of bacteriophage T5 mutants deficient in the ability to induce deoxynucleoside monophosphate kinase.

Two mutants of bacteriophage T5 deficient in the ability to induce wild-type levels of deoxynucleoside monophosphate kinase were isolated and partially characterized. Both mutations were demonstrated to be in a structural gene for the kinase. One of the mutants, designated dnk 10, induces no detectable levels of dCMP, dGMP, or dTMP kinase activity. Because the mutant can successfully infect nonpermissive cells, phage-induced deoxynucleoside monophosphate kinase appears to be an unessential function for phage production. DNA synthesis in dnk 10-infected cells, however, is reduced to 30% of that observed in wild-type-infected cells; phage production is reduced by a comparable amount. The dnk mutation has been mapped and located on the "C" region of the T5 genetic map, 6.3 map units from the C1 locus.

Coliphages↗
PubMed1973

Properties of ribonucleoside diphosphate reductase in nucleotide-permeable cells.

Ribonucleoside diphosphate (RDP) reductase activity can be readily assayed in ether-treated Escherichia coli cells. The rate of cytidine 5'-diphosphate (CDP) reduction observed in ether-treated cells by using saturating substrate concentrations is about 25% of the rate of de novo deoxyribonucleotide synthesis required to account for in vivo deoxyribonucleic acid synthesis. Optimal activity is observed in the presence of magnesium ions and a positive effector. Adenosine 5'-triphosphate (ATP), deoxy ATP (dATP), and deoxythimidine triphosphate serve as positive effectors, and dATP also serves as a negative effector. These effects on the activity in ether-treated cells resemble those observed in vitro with highly purified enzyme. When the RDP reductase activity in these cells is assayed by using high specific activity (3)H-CDP as substrate, even at nonsaturating substrate concentrations, the sensitivity of the assay is sufficient to make it useful for the assay of the low levels of reductase activity in cells not derepressed by thymine starvation or in cells containing mutationally altered RDP reductase. This assay is much easier to perform than the usual in vitro assay, since thioredoxin, thioredoxin reductase, and enzyme subunits B1 or B2 need not be first purified and added to the reaction mixtures.

Adenosine Triphosphate↗