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Biomedical subjects

R A Warren

Publications and source records attributed to R A Warren.

At least 145 records · Page 8Linked to original sources
PubMed1984

Polypeptide synthesis directed by bacteriophage phi W-14 and by mutants defective in DNA synthesis.

The latent period of bacteriophage phi W-14 is approximately 65 min when the doubling time of its host, Pseudomonas acidovorans, is 85 min. Host protein synthesis is shut off relatively slowly, stopping approximately 25 min after infection. There are several phases of phage-specific polypeptide synthesis during the latent period: early polypeptides appear within 10 min after infection; middle polypeptides start to appear between 10 nd 30 min; late polypeptides appear after 30 min. The lengths of time for which individual polypeptides are synthesized vary widely. Several late polypeptides do not appear in the virion. DNA replication is not required for late gene expression. The hypermodified pyrimidine, alpha-putrescinylthymine, appears not to be required in both strands of the DNA duplex for transcription.

Bacteriophages↗
PubMed1984

DNA synthesis in Pseudomonas acidovorans infected with mutants of bacteriophage phi W-14 defective in the synthesis of alpha-putrescinylthymine.

Normal levels of the hypermodified pyrimidine, alpha-putrescinylthymine, which is formed from hydhydroxymethyluracil at the polynucleotide level (Maltman et al., J. Virol. 34:354-359, 1984), are not required in bacteriophage luminal diameterW-14 DNA for the DNA to serve as a replicative template in luminal diameterW-14-infected cells.

Bacteriophages↗
PubMed1984

Why do accident and emergency doctors request X-rays?

A prospective study was carried out to analyse all X-rays requested from the three accident and emergency departments in Sheffield during one week. There were 3253 patients examined, of which 1028 (31.6%) were X-rayed, 1251 sets of X-rays being performed. Few X-rays (4.5%) were requested for medico-legal reasons. Skull X-rays were studied in particular detail. Only 5 (4.5%) of 112 films were subsequently reported as abnormal by the radiologist. The accident and emergency doctor's ability to predict X-ray outcome was not very good, their false positive rate being high at 21% while their false negative rate was low at 5.5%. This indicates that the accident and emergency doctors tended to be over cautious to compensate for their lack of experience.

Emergency Medicine↗
PubMed1983

Bacteriophage phi W-14: the contribution of covalently bound putrescine to DNA packing in the phage head.

Bacteriophage phi W-14 is unusual because its DNA contains 12 mol% of the hypermodified pyrimidine, alpha-putrescinylthymine. The phi W-14 virion is similar in morphology to T4, except that the phi W-14 head is isometric rather than prolate, there is no collar-whisker structure associated with the neck, the tail fibers are short (approximately 15 nm), and the base plate terminates in small plates or knobs rather than spikes. The contractile tail sheath of phi W-14 appears to have a right-handed helical arrangement of subunits with a pitch in the extended form of approximately 20 nm. The "stacked disk" appearance of the tail sheath visible on negatively stained particles has a periodicity of 3-4 nm. The protein shell of the head has a similar thickness (2-3 nm) to that of T4. The phi W-14 virion contains at least 17 different polypeptide species. Based on measurements from electron micrographs of negatively stained phage particles on the same grid square, the volume of the phi W-14 head was estimated to be approximately 72% that of the T4 head. Surprisingly, however, the lengths of the DNA molecules released from phi W-14 and T4 heads by osmotic shock were 59.6 +/- 1.9 and 62.1 +/- 2.4 microns, respectively. am42 is an amber mutant of phi W-14 in which there is only 5 mol% putThy in the DNA made in the nonpermissive host. am42 virions are morphologically normal, but the length of the DNA released from these virions is only 53.1 +/- 3.1 microns. We conclude that phi W-14 DNA is packed much more compactly than T4 DNA into a virion of similar morphology and comparable complexity and that the tight packing is a consequence of, and dependent upon, the presence of putThy in phi W-14 DNA.

Bacteriophages↗
PubMed1983

Formation and possible functions of alpha-putrescinylthymine in bacteriophage phi W-14 DNA: analysis of bacteriophage mutants with decreased levels of alpha-putrescinylthymine in their DNAs.

The DNA synthesized in the nonpermissive host by the noncomplementing mutants am36 and am42 of bacteriophage phi W-14 contains about half the wild-type level of alpha-putrescinylthymine (putThy) and a correspondingly greater level of thymine. The mechanisms whereby thymine nucleotides are excluded from replicating DNA are functional in both mutants because neither of them incorporates exogenous thymidine into DNA. It is proposed that (i) in wild-type phi W-14, the conversion of hydroxymethyluracil to putThy at the polynucleotide level is sequence specific, but that to thymine is nonspecific; and (ii) in the mutants, the sequence-specific recognition is impaired so that more thymine and less putThy are formed. The thymine-rich DNA can be packaged into phage particles. In the case of am42, the phage particles are morphologically indistinguishable from and have essentially the same polypeptide composition as wild-type particles. However, the DNA molecules they contain are about 11% shorter than those in wild-type phage, am42rev4, a revertant of am42, contains DNA with about 70% of the normal level of putThy; these molecules are about 3% shorter than wild-type DNA. The properties of am42 and am42rev4 are consistent with the suggestion that putThy facilitates the very tight packing of phi W-14 DNA (Scraba et al., Virology 124:152-160, 1983). It also appears that the putThy content of phi W-14 DNA can be reduced by no more than 30% without adversely affecting the production of viable progeny; for example, the burst size of am42rev4 is about 25% of that of the wild type.

Bacteriophages↗
PubMed1982

Reactivity of the alpha-putrescinylthymine amino groups in phi W-14 deoxyribonucleic acid.

Bacteriophage phi W-14 DNA contains the hypermodified pyrimidine alpha-putrescinylthymine (putThy) [Kropinski, A. M. B., Bose, R. J., & Warren, R. A. J. (1973) Biochemistry 12, 151]. The primary amino groups of the putrescinyl side chains react with trinitrobenzenesulfonate (TNBS) but at a much slower rate than the reactive lysine side chains of proteins. Both primary and secondary amino groups in the putrescinyl side chains react with acetic anhydride, but the reaction does not go to completion under the conditions employed. Some of the secondary amino groups react faster with acetic anhydride than do some of the primary amino groups. Acetylation lowers the thermal transition temperature (Tm) of phi W-14 DNA, confirming that the unusually high Tm of this DNA is due to the charged putrescinyl groups, but it does not affect the buoyant density. The extent of lowering of the Tm is proportional to the degree of acetylation. Since some of the secondary amino groups are acetylated before some of the primary amino groups, the effect of acetylation on the Tm suggests that both the primary and secondary amino groups can neutralize negative charge repulsion in phi W-14 DNA. Only the putThy residues in the DNA are modified by TNBS and acetic anhydride.

Acetic Anhydrides↗
PubMed1982

Epidemiology of road accidents involving young adults: alcohol, drugs and other factors.

This paper reviews the magnitude and characteristics of the problem of road accidents involving young adults. The magnitude of the problem is considered from the perspective of the contribution of road accidents to mortality and morbidity among young people, relative to other causes. The over-representation of young adults in road accidents is examined to determine the extent to which it occurs as a result of their involvement as drivers, passengers, or as pedestrians. To determine the characteristics of collisions involving young adults, the potential contributory role of alcohol, drugs, and other factors in their collisions is evaluated on the basis of current epidemiological evidence, drawn particularly from studies conducted in Canada. The review examines factors that are related not only to the frequency of collision involvement, but also to the severity of the collision. Although the principal intention of the review is to identify what is known about factors that appear to contribute to accidents involving young adults, an additional purpose is to identify what is not known, and in this context, to suggest, given current methodological and practical limitations, what is capable of being determined in the near term.

Accidents, Traffic↗
PubMed1982

Molecular cloning of a Cellulomonas fimi cellulose gene in Escherichia coli.

A sensitive and simple immunoassay was developed to screen Escherichia coli transformed with recombinant DNA plasmids carrying a cellulase gene. The assay was used to identify a recombinant DNA plasmid carrying at least one cellulase gene from Cellulomonas fimi. The enzyme present in extracts of E. coli carrying the plasmid was active in catalysing the hydrolysis of carboxymethylcellulose as indicated by the production of reducing sugars.

Cellulase↗
PubMed1982

Uptake and fate of bacteriophage phi W-14 DNA in competent Bacillus subtilis.

Phage phi W-14 DNA (in which one-half of the thymine residues are replaced by alpha-putrescinyl thymine) was taken up by competent Bacillus subtilis cells at a rate threefold higher than the rate of homologous DNA uptake. In contrast to other types of heterologous DNA, the amount of phi W-14 DNA taken up in 15 min exceeded the amount of homologous DNA taken up by a factor of two to three, as measured in terms of acid-precipitable material. The amount of phi W-14 DNA taken up was even greater than this analysis indicated if allowance was made for the fact that phi W-14 DNA was degraded more rapidly after uptake than homologous DNA. Competition experiments showed that the affinity of phi W-14 DNA for homologous DNA receptors was lower than the affinity of homologous DNA and was similar to the affinities of other types of heterologous DNA. The more rapid and more extensive uptake of phi W-14 DNA appeared to occur via receptors other than the receptors for homologous DNA, and these receptors (like those for homologous DNA) were an intrinsic property of competent cells. Uptake of phi W-14 DNA was affected by temperature, azide, EDTA, and chloramphenicol, as was uptake of homologous DNA. This was consistent with entry of both DNAs by means of active transport. After uptake, undegraded phi W-14 [3H]DNA was found in the cells in a single-stranded form, whereas a portion of the label was associated with recipient DNA, presumably as a result of incorporation of monomers resulting from degradation. Acetylation of the amino groups of the putrescine side chains in phi W-14 DNA decreased the affinity of this DNA for its receptors without affecting its ability to compete with homologous DNA.

Azides↗
PubMed1982

Isolation and preliminary characterization of amber mutants of bacteriophage phi W-14 defective in DNA synthesis.

Of 42 amber mutants of bacteriophage phi W-14, 6 were defective in DNA synthesis. Three of the mutants synthesized DNA in the nonpermissive host, but were defective in post-replicational modification of the DNA. The DNA synthesized by two of these mutants, am36 and am42, contained more thymine and less alpha-putrescinylthymine than did wild-type DNA; that synthesized by the third mutant, am37, contained the normal amount of thymine, no alpha-putrescinylthymine, and hydroxymethyluracil. The properties of these mutants suggested that the presence of the normal amount of alpha-putrescinylthymine in phi W-14 DNA was essential for the production of viable progeny. Three of the mutants, am6, am35, and am45, failed to synthesize DNA in the nonpermissive host. These mutants were analogous to the DNA off mutants of T4. Nonpermissive cells infected with DNA off mutants accumulated dATP, dGTP, dCTP, and hydroxymethyl dUTP, but not dTTP or alpha-putrescinyldeoxythymidine triphosphate, confirming that both thymine and alpha-putrescinylthymidine in phi W-14 DNA are formed from hydroxymethyluracil at the polynucleotide level. The synthesis of phi W-14 DNA is unusual because (i) thymine is formed from hydroxymethyluracil at the polynucleotide level, (ii) the hypermodification forming alpha-putrescinylthymine is essential, and (iii) thymine and alpha-putrescinylthymine must be made in the correct proportions. Complementation tests showed that the mutants defined three genes involved in DNA polymerization and two genes involved in post-replicational modification.

Bacteriophages↗
PubMed1982

Incidence and toxicological aspects of drugs detected in 484 fatally injured drivers and pedestrians in Ontario.

Results are presented of a comprehensive drug study carried out on specimens from drivers and pedestrians fatally injured in Ontario. Toxicological analyses were regularly performed on blood and urine and occasionally on vitreous humor, stomach contents, and liver. The analytical procedures could detect and quantitate a wide variety of drugs including such illicit drugs as Cannabis. With respect to drivers, alcohol was found in 57% of the study sample and drugs other than alcohol, in 26%. However, in only 9.5% of the drivers were psychoactive drugs (other than alcohol) detected in the blood in concentrations that may adversely affect driving skills. Delta-9-Tetrahydrocannabinol and diazepam accounted for a majority of the findings in this category.

Accidents, Traffic↗
PubMed1981

5-[(Hydroxymethyl)-O-pyrophosphoryl]uracil, an intermediate in the biosynthesis of alpha-putrescinylthymine in deoxyribonucleic acid of bacteriophage phi W-14.

In a nonpermissive host, an amber mutant, am 37, of bacteriophage phi W-14 synthesizes deoxyribonucleic acid (DNA) of considerably greater buoyant density than the DNA synthesized by wild-type phage. The am 37 DNA lacks the hypermodified pyrimidine, alpha-putrescinylthymine (putThy). Instead, it contains a new modified base, 5-[(hydroxymethyl)-O-pyrophosphoryl]uracil (hmPPUra). Extracts of cells infected with wild-type phi W-14 convert the hmPPUra in am 37 DNA to putThy when incubated with putrescine.

Bacteriophages↗
PubMed1981

Ionized calcium in acute pancreatitis and its relationships with total calcium and serum lipase.

Serial measurements of serum amylase, lipase and ionized calcium were made in a prospective study of 17 patients with acute pancreatitis. The mean serum ionized calcium was significantly below the normal range for the first 24 h and had returned to normal after 48 h. There was no correlation between serum ionized calcium and paired calcium corrected for albumin during the first 36 h of the study, but they were correlated for the remainder of the investigation. Serum lipase and ionized calcium levels were just significantly correlated over the first 3 days (r = -0.44; t = 2.3; P less than 0.05; d.f. 22), but failed to reach correlation over the whole period of study (r = -0.34; t = 2.0; d.f. 31). These data establish a significant drop in directly measured ionized calcium early in an attack of pancreatitis, which is not seen in the paired corrected calcium values. Furthermore, the drop is correlated with serum lipase, although this is weak and other factors must be involved in the hypocalcaemia.

Acute Disease↗
PubMed1981

Phi W-14 DNA inhibits transfection of Bacillus subtilis by SPP1 DNA.

The DNA of bacteriophage phi W-14 is unusual in that half of the thymine residues are replaced with the hypermodified pyrimidine alpha-putrescinylthymine (Kropinski et al., Biochemistry 12:151-157, 1973). Bacteriophage phi W-14 DNA and Bacillus subtilis DNA exhibited comparable competing abilities for the uptake of transfecting bacteriophage SPP1 DNA by competent cells of B. subtilis. B. subtilis DNA decreased transfection and uptake to the same extent, indicating that it merely competed with SPP1 DNA for uptake. Phi W-14 DNA, however, decreased transfection up to 30 times more effectively than it inhibited uptake. Phi W-14 DNA did not alter the kinetics of transfection. The degree of inhibition of transfection was dependent upon the time of addition of Phi W-14 DNA relative to the time of addition of SPP1 DNA. If failed to inhibit when added 30 min after SPP1 DNA. It had a fourfold-greater effect when added 10 min before, rather than simultaneously with, SPP1, but this enhancement was abolished by high concentrations of SPP1 DNA. The nature of the transfection process was not altered in those cells escaping inhibition by Phi W-14 DNA: two molecules of transfecting SPP1 DNA were required to form a transfectant with or without Phi W-14 DNA. Free putrescine did not affect transfection by SPP1 DNA. It was concluded that the putrescine groups covalently attached to phi W-14 DNA allowed this DNA to interfere with the transfection process at the intracellular level.

Bacillus subtilis↗