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Biomedical subjects

R E Glass

Publications and source records attributed to R E Glass.

At least 37 records · Page 2Linked to original sources
PubMed1988

Assembly of amber fragments of the beta subunit of Escherichia coli RNA polymerase.

Immunoblotting of size-separated whole cell proteins permitted the study of protein-protein interaction. Briefly, proteins obtained from cleared cell lysates of Escherichia coli were separated by glycerol gradient centrifugation and analysed by blotting against a set of specific antibodies. We have applied this procedure to the assembly of 11 N-terminal amber fragments of the beta subunit of E. coli RNA polymerase ranging in size between 97% and 23% the length of the intact beta polypeptide (1342 amino acids). In this way, we have been able to define regions on the beta polypeptide involved in the assembly of RNA polymerase.

Centrifugation, Density Gradient↗
PubMed1988

Cloning and characterization of the genes for the two homocysteine transmethylases of Escherichia coli.

We have cloned the genes for the two homocysteine transmethylases of Escherichia coli K12. The vitamin B12-independent enzyme is encoded by the metE gene while the metH gene codes for the vitamin B12-requiring enzyme. Overexpression of the gene products and Tn1000 mutagenesis have enabled the metE and metH gene products to be identified as 99 kDa and 130 kDa polypeptides, respectively. The truncated polypeptides generated by Tn1000 insertion were used to determine the direction of transcription of the metE and metH genes. Negative complementation suggests that the MetH enzyme exists as an oligomer. Investigation of the expression of the chromosomal- and plasmid-encoded gene products confirms that metE is subject to negative control by vitamin B12 and methionine, and that metH is under positive control by the cofactor and negative control by methionine. For vitamin B12 and methionine to act as regulatory effectors in metE control, functional metH and metJ genes are required, respectively. The use of stable Tn1000-generated fragments of the metE product as electrophoretic markers for the plasmid-encoded metE gene product demonstrated that the two regulatory proteins involved in negative control of metE are present in excess. Under conditions whereby both forms of negative metE control are non-functional, the metE gene product represented about 90% of the total protein, and cell growth was severely impaired.

Cloning, Molecular↗
PubMed1987

Subunit assembly and metabolic stability of E. coli RNA polymerase.

Immunological cross-reaction was employed for identification of proteolytic fragments of E. coli RNA polymerase generated both in vitro and in vivo. Several species of partially denatured but assembled RNA polymerase were isolated, which were composed of fragments of the two large subunits, beta and beta', and the two small and intact subunits, alpha and sigma. Comparison of the rate and pathway of proteolytic cleavage in vitro of unassembled subunits, subassemblies, and intact enzymes indicated that the susceptibility of RNA polymerase subunits to proteolytic degradation was dependent on the assembly state. Using this method, degradation in vivo was found for some, but not all, of the amber fragments of beta subunit in merodiploid cells carrying both wild-type and mutant rpoB genes. Although the RNA polymerase is a metabolically stable component in exponentially growing cells of E. coli, degradation of the full-sized subunits was found in two cases, i.e., several temperature-sensitive E. coli mutants with a defect in the assembly of RNA polymerase and the stationary-phase cells of a wild-type E. coli. The in vivo degradation of RNA polymerase was indicated to be initiated by alteration of the enzyme structure.

Cell Cycle↗
PubMed1987

Multivalent regulation of the nusA operon of Escherichia coli.

The rate of synthesis and intracellular content of the NusA protein, a transcription termination factor, were determined for wild-type and nusA and/or nusB mutants of Escherichia coli. Both the rate and content of NusA in wild-type strains were similar to that of the RNA polymerase sigma subunit, a transcription initiation factor, on a molar basis, and about 30%-40% the levels of RNA polymerase beta beta' subunits. At the stationary phase of cell growth, the values increased in parallel for both transcription factors up to approximately the level of the beta beta' subunits. In nus mutants, the rate of synthesis and the content of the sigma subunit were significantly increased. These observations together suggest that the two transcription factors are coordinately regulated.

Bacterial Proteins↗
PubMed1987

Hierarchy of the strength of Escherichia coli stringent control signals.

The quantitative effect of ppGpp, the effector of stringent control, on various Escherichia coli promoters was measured in an in vitro mixed transcription system. This allowed us to determine, among these promoters, the hierarchy of promoters according to their ppGpp susceptibility. The strength of the stringent control signal, however, was found to be altered when the test promoters were transcribed by ppGpp-insensitive RNA polymerases from relaxed mutants of E. coli, which carry substitutions in the beta subunit gene (rpoB). Thus, it was concluded that the activity of the stringent control signal depends on the nature of the RNA polymerase as well as that of the promoter.

DNA-Directed RNA Polymerases↗
PubMed1987

Surgical audit in a district general hospital: a stimulus for improving patient care.

A computerised audit system was used to monitor clinical and administrative management of surgical patients in a District General Hospital. In one year (1985) there were 1,060 discharges from 27 beds (39.3 patients/bed/year). Operative treatment was required in 652 patients but 408 patients did not undergo surgery. Of this latter group the majority were admitted with abdominal pain (179 patients) and a final diagnosis was made in only 76 patients. The majority of patients were discharged within one week of admission, but 94 patients (8.9%) were admitted for more than three weeks. Of this group 42.5% could not be discharged because of poor home and social circumstances. The results of this study suggest that management could be improved without compromising patient care, in particular by providing adequate facilities for day care surgery and by improving social and geriatric support services. Reductions in staff or bed numbers without providing such improvements will lead to a significant reduction in patient care.

Adult↗
PubMed1986

Genetic studies on the beta subunit of Escherichia coli RNA polymerase. VII. RNA polymerase is a target for ppGpp.

RNA polymerase was isolated from two suppressed rpoB amber strains exhibiting relaxed control over RNA synthesis in vivo. In vitro transcription analysis of these mutant holoenzymes carrying defined substitutions at known sites in the beta subunit clearly shows that single amino acid changes in beta render RNA polymerase resistant to ppGpp. This unambiguously demonstrates that RNA polymerase is indeed the target for ppGpp.

DNA Restriction Enzymes↗
PubMed1986

Genetic studies on the beta subunit of Escherichia coli RNA polymerase. VIII. Localisation of a region involved in promoter selectivity.

We have previously isolated an E. coli derivative carrying a small internal deletion (delta(rpoB)1570-1) of the beta structural gene. This RNA polymerase deletion mutant has no noticeable phenotype other than a slightly increased generation time in minimal medium. The deletion, which removes about 165 bp, has been localised to between codons 965 and 1,083, indicating it excises part of a tandem repeat structure present in the C-terminal region of beta. Analysis in vitro of purified RNA polymerase from the deletion mutant indicates that this enzyme has an altered promoter selectivity. These observations allow localisation of a site on the beta polypeptide of E. coli RNA polymerase involved in transcriptional initiation.

DNA-Directed RNA Polymerases↗
PubMed1986

Genetic studies on the beta subunit of Escherichia coli RNA polymerase. IX. The role of the carboxy-terminus in enzyme assembly.

The assembly of RNA polymerase was studied in Escherichia coli mutants encoding large N-terminal amber fragments of the beta subunit. Whereas the removal of up to 20% of the carboxy-terminus does not prevent the formation of premature core enzyme, the amber fragments seem to interfere with holoenzyme production. These studies permit, therefore, the localization of a region on the beta polypeptide involved in sigma binding.

DNA-Directed RNA Polymerases↗
PubMed1986

The results of surgical treatment of cancer of the colon at the Cleveland Clinic from 1965-1975: classification of the spread of colon cancer and long-term survival.

Between the years 1965-1975, 564 patients underwent surgical treatment for cancer of the colon. The primary tumour was removed in 502 patients (89%) in all cases with a "no touch isolation" technique. The 5-year survival rate corrected for age was 64% in 546 operative survivors, and 82% in 413 patients operated with intent to cure. Survival analyses are presented classifying the spread of the tumour by the clinico-pathological method of Turnbull, the TNM method, the Astler-Coller method, Dukes' method. The results suggest that the Astler-Coller classification offers no advantage over that of Dukes' when predicting survival for patients after operation for cure, and that separating those patients considered to have evidence of invasion of an adjacent organ at operation (Turnbull's classification) from those patients without evidence of contiguous growth, is only justified if invasion of cancer is confirmed by histological examination of the resected specimen.

Adult↗
PubMed1986

Investigation of the regulation of the Escherichia coli btuB gene using operon fusions.

Operon fusions were isolated between Mu dX (lac CmR ApR) and btuB, the gene encoding the multivalent vitamin B12 outer membrane receptor. Using these fusions, vitamin B12-mediated repression of btuB in Escherichia coli was demonstrated. Mutations in metH, metE and ompR as well as exogenous methionine, membrane pertubants, high osmolar conditions and temperature had no major effect on the expression of the btuB gene.

Escherichia coli↗
PubMed1986

Plasma arginine in cancer of the gastrointestinal tract: effect of surgical treatment.

The concentration of 21 amino acids was measured in the venous plasma of 41 patients with cancer of the gastrointestinal tract who had lost weight, 12 patients who had lost a similar amount of weight from non-malignant, non-septic conditions (benign weight loss), 12 patients with cancer of the gastrointestinal tract who had not lost weight and 21 control patients. Sixteen patients with localised tumours were restudied eight and 12 weeks after successful removal of the primary growth. Six patients with pyloric stenosis (benign weight loss) were similarly studied for comparison after corrective surgery. The concentration of the amino acid arginine was significantly greater in patients with cancer both with weight loss (71.2 +/- 4.1 mumol/l mean +/- SEM) and without weight loss (66.8 +/- 4.1 mumol/l) when compared both with patients with benign weight loss (34.6 +/- 3.2 mumol/l) and with control patients (48.2 +/- 3.5 mumol/l) (p less than 0.05). In patients with cancer subjected to surgery the concentration of arginine (76.4 +/- 7.5 mumol/l) fell to normal levels eight weeks after operation and remained normal 12 weeks after surgery (48.6 +/- 4.4 mumol/l) (p less than 0.05). This was in contrast with the rise in plasma arginine in patients with pyloric stenosis after surgery, suggesting that the raised level of arginine was due to the presence of the primary tumour.

Amino Acids↗
PubMed1985

The results of surgical treatment of cancer of the rectum by radical resection and extended abdomino-iliac lymphadenectomy.

At St Mark's Hospital survival after radical surgery for cancer of the rectum has not changed significantly over the past 30 years. The technique of extended abdomino-iliac lymphadenectomy was developed in an attempt to improve prognosis in patients considered to have particularly unfavourable tumours. Between 1960 and 1981 the technique was used in 75 patients with a single adenocarcinoma of the rectum. Two patients died postoperatively and 52 patients developed complications; a mortality and morbidity similar to those seen after conventional surgery at this hospital. Five-year survival rate showed no improvement over that achieved by conventional techniques; disappointingly this was also the case for patients with Dukes' C1 tumours. The results of this study suggest that an improvement in survival in patients with cancer of the rectum is unlikely to be achieved by any extension of conventional radical surgery.

Abdomen↗