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Biomedical subjects

A J Russell

Publications and source records attributed to A J Russell.

At least 73 records · Page 4Linked to original sources
PubMed1992

Solubilization and activity of proteins in compressible-fluid based microemulsions.

We have used the pressure dependency of density in near critical propane to design a novel protein extraction system. Active, structurally intact, proteins have been extracted from an aqueous phase into subcritical propane containing the non-ionic detergent polyoxyethylene sorbitan trioleate (Tween-85). The pressure dependence of protein transfer from the aqueous to organic phase is described for cytochrome C and subtilisin. The effect of the microemulsion and compressible propane on protein structure and function is also discussed. The first determinations of kinetic constants for an enzyme-catalyzed reaction in such a system are also presented.

Cytochrome c Group↗
PubMed1991

Theatre over-shoes do not reduce operating theatre floor bacterial counts.

Occasional staff or visitors to operating theatres are usually requested to don over-shoes as this is perceived to reduce bacterial floor colony counts. However, this entails some expense and considerable inconvenience. Using disposable surface contact plates floor bacterial counts were measured four times a day at five different sites during the 5 normal working days of one 2-week period in a general operating theatre when over-shoes were worn and one 2-week period when over-shoes were not worn. There was no significant difference in the mean bacterial floor colony counts between the two periods according to sampling times or sites. As in Intensive Therapy units, over-shoes should no longer be used in general operating theatres.

Bacteria↗
PubMed1991

The effect of surgical theatre head-gear on air bacterial counts.

The wearing of disposable head-gear in operating theatres is currently recommended for scrubbed and non-scrubbed staff. However, there is little evidence of its effectiveness as an infection control measure in casual or non-scrubbed theatre staff. The effect of head-gear on bacterial air counts was studied, using six volunteers, in a sealed room, with and without ventilation. Using a Casella slit sampler and a SAS Air Sampler, air counts ranged from 0.08 to greater than 2.9 colony forming units (cfu) m-3. The wearing of head-gear was not associated with a reduction in air counts but counts were lower with ventilation. We recommend that non-scrubbed staff no longer wear head-gear as effective ventilation probably counteracts any possible increased bacterial shedding. Scrubbed staff should continue to wear disposable head-gear because of their proximity to the operative field.

Air Microbiology↗
PubMed1989

Antibody-antigen binding in organic solvents.

We describe, for the first time, the action of antibodies in anhydrous organic solvents. It has been demonstrated that the binding of a hapten, 4-aminobiphenyl, to the immobilized monoclonal antibody 2E11 is strong and specific not only in water but also in a variety of non-aqueous media. Further, the strength of interaction between antibody and hapten has been related to the hydrophobicity of the solvent: the more hydrophobic the solvent, the weaker the protein-ligand interaction.

Aminobiphenyl Compounds↗
PubMed1988

Inhibitor-induced enzyme activation in organic solvents.

The enzymatic activity of the protease subtilisin in anhydrous organic solvents can be dramatically increased by pretreating the enzyme before it is placed in the nonaqueous medium. For instance, lyophilization of subtilisin from aqueous solution containing competitive inhibitors (followed by their removal) created an enzyme which was up to 100 times more active than the enzyme lyophilized in the absence of such ligands. This phenomenon of ligand-induced "enzyme memory" also extends to the stability, affinity, and substrate specificity of subtilisin in organic solvents.

Binding, Competitive↗
PubMed1987

Electrostatic effects on modification of charged groups in the active site cleft of subtilisin by protein engineering.

The dielectric constant in the active site cleft of subtilisin from Bacillus amyloliquefaciens has been probed by mutating charged residues on the rim and measuring the effect on the pKa value of the active site histidine (His64) by kinetics. Mutation of a negatively charged surface residue, which is 12 to 13 A from His64, to an uncharged one Asp----Ser99) lowers the pKa of the histidine by up to 0.4 unit at low ionic strength (0.005 to 0.01 M). This corresponds to an apparent dielectric constant of about 40 to 50 between Asp99 and His64. The mutation is in an external loop that is known to tolerate a serine at position 99 from homologies with subtilisins from other bacilli. The environment between His64 and Asp99 is predominantly protein. Another charged residue that is at a similar distance from His64 (14 to 15 A) and is also in an external loop that is known to tolerate a serine residue is Glu156, at the opposite side of the active site. There is only water in a direct line between His64 and Glu156. Mutation of Glu----Ser156 also lowers the pKa of His64 by up to 0.4 unit at low ionic strength. This change again corresponds to an apparent dielectric constant of about 40 to 50. The pKa values were determined from the pH dependence of kcat/KM for the hydrolysis of peptide substrates, with a precision of typically +/- 0.02 unit. The following suggests that the changes in pKa are real and not artefacts of experimental conditions: Hill plots of the data for pKa determination have gradients (h) of -1.00(+/- 0.02), showing that there are negligible systematic deviations from theoretical ionization curves involving a monobasic acid: the pH dependence for the hydrolysis of two different substrates (succinyl-L-alanyl-L-alanyl-L-prolyl-L-phenylalanyl p-nitroanilide and benzoyl-L-valyl-L-glycyl-L-arginyl p-nitroanilide) gives identical results so that the pKa is independent of substrate; the pH dependence is unaffected by changing the concentration of enzyme, so that aggregation is not affecting the results; the shift in pKa is masked by high ionic strength, as expected qualitatively for ionic shielding of electrostatic interactions.

Amino Acid Sequence↗
PubMed1987

Transmission electron microscopy of percutaneous fine needle aspirates from lung: a study of 70 cases.

Seventy consecutive lung fine needle aspirates (FNA) from 69 patients were examined by cytology/cell block histology, by transmission electron microscopy (TEM), and, where available, at histological follow up to determine the value of TEM in interpreting lung FNAs. Of 70 FNAs, 50 were suitable for TEM. Transmission electron microscopy was helpful in classifying seven of 10 poorly differentiated tumours, and two case histories are reported. In 26 of 30 well differentiated tumours TEM confirmed diagnosis by light microscopy. Two TEM false negatives, but no TEM false positives, were recorded. It is concluded that transmission electron microscopy of cells aspirated from lung can be helpful when unequivocal diagnosis has not been achieved.

Aged↗
PubMed1986

Peritoneal cystic mesothelioma: an electron microscopic and immunohistochemical study of two male patients.

The clinical, pathological, and ultrastructural features of two cases of peritoneal cystic mesothelioma occurring in men were studied. The results of immunohistochemical staining for CAM 5.2, epithelial membrane antigen, carcinoembryonic antigen, and Factor VIII related antigen are reported for the first time and compared with the staining results of two peritoneal cystic lymphangiomas. Although resembling cystic lymphangioma by light microscopy, cystic mesothelioma may have a greater tendency for local recurrence. Staining for CAM 5.2 or epithelial membrane antigen may facilitate the differentiation of these two entities.

Adult↗
PubMed1976

Digoxin pharmacokinetics: multicompartmental analysis and its clinical implications.

The kinetics of digoxin have been investigated in healthy volunteers using an isotopic tracer technique. A three compartment open kinetic model has been proposed as the simplest model consistent with the plasma, urinary and faecal data obtained. The renal clearance of digoxin (mean +/- s.d.) was found to be 119+/-10 ml/min, which did not differ significantly from the glomerular filtration rate (110+/-14 ml/min). Digoxin extra-renal clearance (mean+/-s.d.) was found to be 47+/-7 ml/min. The model predicts that the tissue concentration attained after four 0.25 mg oral doses spread over 24 h can be achieved within a period of 4 h following a single oral loading dose of 1 mg. Maintenance doses can be derived from a simple formula based on the glomerular filtration rate, extra-renal clearance and bioavailability of the digoxin preparation used.

Adult↗