Search PubMed⌕ Search

Biomedical subjects

S Cooper

Publications and source records attributed to S Cooper.

At least 397 records · Page 22Linked to original sources
PubMed1966

Utilization of d-Methionine by Escherichia coli.

Cooper, Stephen (University Institute of Microbiology, Copenhagen, Denmark). Utilization of d-methionine by Escherichia coli. J. Bacteriol. 92:328-332. 1966.-Methionine-requiring strains of Escherichia coli grow on d-methionine. Mutants can be isolated which cannot grow on d-methionine. The d-methionine nonutilizing mutation is independent of the methionine requirement, and maps near the lac region of the E. coli genome. Growth of methionine-requiring strains on d-methionine is dependent upon aerobic conditions. Cells grown on d-methionine have a sixfold greater ability to incorporate d-methionine into protein than cells grown on l-methionine. The incorporation of d-methionine is inhibited by l-methionine.

Journal Article↗
PubMedDate not supplied

Comparison of the performance of anti-CD7 and anti-CD38 bispecific antibodies and immunotoxins for the delivery of saporin to a human T-cell acute lymphoblastic leukemia cell line.

We have investigated the cytotoxic performance of two different anti-CD7/anti-saporin BsAb's (HB2 x DB7-18 and Q1.1), three anti-CD38/anti-saporin BsAb's (OKT10 x RabSap, OKT10 x DB7-18 and Q4.1) and an anti-CD7 (HB2-Sap) and anti-CD38-saporin (OKT10-Sap) immunotoxin for delivering the ribosome inactivating protein (rip) to the human T-cell acute lymphoblastic leukemia cell line HSB-2. In the case of CD7 as target molecule the immunotoxin outperformed both anti-CD7 BsAb's being six times more effective than HB2 x DB7-18 and 98 times more so than Q1.1 at effectively inhibiting protein synthesis in a dose dependent manner. The chemically constructed HB2 x DB7-18 BsAb was more effective at inhibiting protein synthesis and cell growth in target HSB-2 cells in a dose dependent manner than the quadroma produced BsAb Q1.1. Both BsAb demonstrated a prozone effect used at concentrations above 0.1 nM though this was more pronounced for Q1.1 than for HB2 x DB7-18. The prozone effect was partially though not completely reversed by increasing the concentration of saporin in the system. In the case of CD38 as target molecule the anti-CD38 IT OKT10-Sap performed poorly, never actually achieving its IC50. Two BsAb's constructed with monoclonal anti-saporin Fab arms each recognizing a different epitope on the saporin molecule also performed poorly. In contrast the BsAb OKT10 x RabSap constructed with Fab derived from a rabbit polyclonal anti-saporin antiserum performed in a dose dependent manner achieving its IC50 at a concentration of 1.3 nM. This BsAb also exhibited a prozone effect. These results exemplify the importance of cross linking adjacent target molecules on the cell surface in order to achieve effective delivery of saporin to the cell interior.

ADP-ribosyl Cyclase↗
PubMedDate not supplied

Primary intraventricular cardiac tumors in children: contemporary diagnostic and management options.

We reviewed the intraventricular cardiac tumors presenting at our institution between 1985-1991, studying the presentation, modes of investigation, and evidence of hemodynamic compromise. Thirteen patients presented with intraventricular tumors during the study period. Two of the tumors were rhabdomyosarcomas, one was a myxoma, and 10 were rhabdomyomas. All patients were evaluated with two-dimensional and pulsed Doppler echocardiography and B-color imaging was undertaken in three patients. Four patients presented for elective scans to complement investigations for tuberous sclerosis, seven patients had cardiac symptoms, and two patients presented prenatally. Obstruction to intracardiac flow was present in five patients. Two patients had the tumor excised and one had an open biopsy of the tumor. One patient had an transvascular biopsy at cardiac catheter. Early detection of cardiac tumors is increasing, particularly rhabdomyomas. With fetal echocardiography, more patients should come to attention prenatally. B-color may be useful addition in assessing cardiac tumors, aiding detection and definition of intramural lesions.

Child↗
PubMedDate not supplied

Replication of mini-F plasmids during the bacterial division cycle.

The cell-cycle replication patterns of two mini-F plasmids have been examined using the membrane-elution technique (to produce cells labelled at different times during the division cycle) and scintillation counting (for quantitative analysis of radioactivity incorporated into plasmid DNA). The mini-F plasmid pML31, which contains the oriV and oriS origins of replication, replicates in a cell-cycle-specific manner with a pattern and cell-cycle timing similar to the parental F plasmid. The mini-F plasmid pMF21, deleted for the region containing the oriV origin of replication, replicates more randomly throughout the division cycle. These results suggest that the oriV origin of replication may be related to cell-cycle-specific replication of the F plasmid.

Cell Division↗
PubMedDate not supplied

Effect of mecillinam on peptidoglycan synthesis during the division cycle of Salmonella typhimurium 2616.

The effects of mecillinam, ampicillin and cephalexin on peptidoglycan synthesis in Salmonella typhimurium 2616 have been studied at equivalent concentrations or "isoactivities". Using antibiotics at isoactivities allows a direct comparison of the biochemical effects of different antibiotics. When mecillinam was added at different times during the division cycle at a concentration that produced 50% inhibition of peptidoglycan synthesis in an exponential culture over a short period of time, the inhibition of synthesis was greatest in the newborn cells and least in the dividing cells. Antibiotic competition experiments showed that mecillinam preferentially bound to penicillin-binding protein 2 in S. typhimurium 2616. High performance liquid chromatography analysis of the residual peptidoglycan synthesized in the presence of mecillinam showed an unexpected increase in pentapeptides and a significant increase in cross-linking. Other antibiotics added at equivalent activities did not show an increase in cross-linking.

Amdinocillin↗