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D C Low

Publications and source records attributed to D C Low.

8 recordsLinked to original sources
PubMed1992

Expression, purification and characterization of a mouse-human chimeric antibody and chimeric Fab' fragment.

B72.3 is a mouse monoclonal antibody against a tumour-associated antigen, TAG72, which recognizes breast, ovarian and colorectal tumour tissue. A mouse-human chimeric version of B72.3 has been expressed in Chinese-hamster ovary cells. This molecule has the binding specificity of B72.3 and constant regions from human IgG4. The chimeric B72.3 assembles to intact IgG and recognizes TAG72 as well as B72.3 in competitive binding assays. A proportion of the chimeric B72.3 (approx. 10%) does not form inter-heavy-chain disulphide bonds but still assembles into the IgG tetramer. This appears to be a general property of human IgG4 molecules. Co-expression of the chimeric light chain with a chimeric Fd' gene resulted in the expression of functional Fab'. Very little F(ab')2 is produced, although the Fab' can be oxidized to the dimeric F(ab')2 in vitro. The production of Fab' and F(ab')2 by this method is an attractive alternative to proteolytic digestion of IgG. The ability to produce these molecules in large quantities will allow the production and testing of a range of anti-tumour antibody and antibody fragment conjugates.

Animals↗
PubMed1991

Crystallization and preliminary X-ray diffraction study of a chimaeric Fab' fragment of antibody binding tumour cells.

Crystals have been obtained of a chimaeric Fab' fragment that binds to a tumour-associated mucin-like glycoprotein TAG72. The Fab' fragment comprises the variable heavy and light-chain domains of a murine monoclonal antibody, B72.3, coupled to human gamma 4 and kappa constant regions. The crystals are orthorhombic and belong to the space group P2(1)2(1)2(1), with unit cell dimensions a = 67.9 A, b = 94.2 A and c = 208.8 A. Diffraction to 2.6 A resolution was observed using synchrotron radiation. Despite the acute radiation sensitivity of the crystals a full native data set has been collected using the Weissenberg camera at the Photon Factory synchrotron. These data will be used for molecular replacement calculations in an attempt to elucidate the structure of this chimaeric Fab' fragment.

Animals↗
PubMed1987

Involvement of a low-molecular-weight substance in in vitro activation of the molybdoenzyme respiratory nitrate reductase from a chlB mutant of Escherichia coli.

The soluble subcellular fraction of a chlB mutant contains an inactive precursor form of the molybdoenzyme nitrate reductase, which can be activated by the addition to the soluble fraction of protein FA, which is thought to be the active product of the chlB locus. Dialysis or desalting of the chlB soluble fraction leads to the loss of nitrate reductase activation, indicating that some low-molecular-weight material is required for the activation. The protein FA-dependent activation of nitrate reductase can be restored to the desalted chlB soluble fraction by the addition of a clarified extract obtained after heating the chlB soluble fraction at 100 degrees C for 8 min. The heat-stable substance present in this preparation has a molecular weight of approximately 1,000. This substance is distinct from the active molybdenum cofactor since its activity is unimpaired in heat-treated extracts prepared from the organism grown in the presence of tungstate, which leads to loss of cofactor activity. Mutations at the chlA or chlE locus, which are required for molybdenum cofactor biosynthesis, similarly do not affect the activity of the heat-treated extract in the in vitro activation process. Moreover, the active material can be separated from the molybdenum cofactor activity by gel filtration. None of the other known pleiotropic chlorate resistance loci (chlD, chlG) are required for the expression of its activity. Magnesium ATP appears to have a role in the formation of the active substance. We conclude that a low-molecular-weight substance, distinct from the active molybdenum cofactor, is required to bestow activity on the molybdoenzyme nitrate reductase during its biosynthesis.

Adenosine Triphosphate↗
PubMed1987

Birthweight-specific risk factors for necrotising enterocolitis.

In a multicentre case-control study of necrotising enterocolitis risk factors were found to vary with birthweight of cases. In very low birthweight cases the risk factors identified were those associated with prolonged or recurrent hypoxia (recurrent apnoea, respiratory distress, assisted ventilation, and umbilical artery catheterisation). In heavier birthweight infants the risk factors were, in contrast, related to hypoxia at birth (low 1 minute Apgar score and endotracheal intubation at birth) and umbilical vessel catheterisation used in exchange transfusions. Contradictory findings in published case-control studies carried out in the USA may be due to differences in patient populations and management policies. Hypoxia and umbilical vessel catheterisation should still be considered as risk factors for necrotising enterocolitis.

Apgar Score↗
PubMed1985

Ceftazidime in neonatal infections.

Ninety one neonates received 108 courses of intravenous ceftazidime (25 mg/kg, 12 hourly) over a study period of 15 months. Fourteen had clinically and bacteriologically proved infections. Only one of these had resistant organisms. Four (two with group B beta haemolytic streptococcal infections, one with Escherichia coli meningitis, and one with Staphylococcal aureus septicaemia) failed to respond despite adequate treatment. Bacteriological eradication or clinical improvement, or both, were obtained in the remaining nine. Routine biochemical and haematological values were monitored and there were no side effects. High serum ceftazidime concentrations, well exceeding the minimum inhibitory concentration for most common neonatal pathogens were obtained and maintained throughout treatment. Penetration into the cerebrospinal fluid was excellent in eight of the nine cases studied. Ceftazidime has a theoretical role as a broad spectrum antibiotic suitable for neonatal use with no evident side effects. In this study, however, it was only appropriate for Gram negative infections, and was ineffective against Gram positive organisms. Ceftazidime cannot therefore be recommended as monotherapy before the results of bacteriological culture are known.

Bacterial Infections↗