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Biomedical subjects

S Dunn

Publications and source records attributed to S Dunn.

16 recordsLinked to original sources
PubMed1992

Epitope mapping of monoclonal antibodies to the Escherichia coli F1 ATPase alpha subunit in relation to activity effects and location in the enzyme complex based on cryoelectron microscopy.

The interaction of Escherichia coli F1 ATPase (ECF1) with several different monoclonal antibodies (mAbs) specific for the alpha subunit has been examined. The epitopes for each of the mAbs have been localized by using molecular biological approaches to generate fragments of the alpha subunit. The binding of several of the mAbs has also been examined by cryoelectron microscopy of ECF1 Fab complexes. One of the mAbs, alpha II, bound in the region Asn 109-Val 153 without affecting ATPase activity. Most of the mAbs bound in the C-terminal third of the alpha subunit. MAb alpha 1 bound between residues Gln 443 and Trp 513. This mAb activated ATPase activity and was visualized in cryoelectron microscopy, superimposed on the alpha subunit, indicating that the epitope was on the top or bottom of ECF1 in the hexagonal projection. Other mAbs to the C-terminus, including alpha D which also activated the enzyme, reacted between Gly 371 and Trp 513 but failed to bind to small overlapping fragments within this sequence. The epitopes for these mAbs are probably formed by the folded polypeptide which occurs only in Western analysis when long stretches of the alpha subunit are present, suggesting that the C-terminus of alpha is a self-folding domain. In cryoelectron microscopy, Fab fragments for alpha D were seen extending from the sides of the ECF1 complex in hexagonal projection.

Antibodies, Monoclonal↗
PubMed1992

Comparative studies of isolated CD3: CD8, CD3: CD3, and monovalent CD3 binding on CD8+ T-cell activation: model of progressive T-cell receptor aggregation synergism.

The TCR and CD8 complexes of CD8+ T cells bind to different regions of MHC class I molecules and both play important roles in the response of the CD8+ T cells to Ag/MHC on APCs. In this report, we mimicked common MHC binding with an anti-CD3:anti-CD8 (CD3,8) BSMAB to isolate the effect of CD3: CD8 pairing, compared this with the effect of CD3: CD3 pairing by the parental bivalent anti-CD3 MAB, and with monovalent anti-CD3 binding by an anti-CD3: anti-CD4 (CD3,4) BSMAB. CD3: CD8 pairing induced an increase in cytosolic free [Ca2+] 1.5 to 3.0-fold greater than the increase induced by CD3: CD3 pairing whereas monovalent CD3 binding induced only 20%-30% of the increase. Postbinding receptor migration studies suggested that microaggregation increased from monovalent CD3 binding to CD3: CD3 pairing to CD3: CD8 pairing. Further studies revealed that progressively higher concentrations of antibodies were needed from CD3,8 to CD3,3 to CD3,4 to initiate the same degree of DNA synthesis. These results demonstrated that Ti/CD3 and CD8 can indeed be bridged by a single molecule. A model of direct CD8: CD3 synergism was raised as a possible explanation for the enhanced activation induced by CD3: CD8 pairing. The observed parallel between all three parameters and the number of TCRs that can be directly linked by the Abs raised a nonmutually exclusive model whereby CD3 binding induces activated TCR intermediaries (aTCRi) that progressively synergize with other adjacent aTCRis. In this model, this dominant inter-aTCRi synergism may be enhanced by the di- and multimeric CD8 alpha chains serving as aTCRi-aggregation foci.

Antigen-Antibody Reactions↗
PubMed1992

Urinary tract infections in children with posterior urethral valves after kidney transplantation.

The records of 14 boys with posterior urethral valves who had renal failure and subsequently underwent renal transplantation were reviewed to determine the postoperative incidence of urinary tract infection relative to that of 29 male transplant children without valves, who served as controls. There were no significant differences between the posterior urethral valve patients and controls with regard to age, donor source, immunosuppression, followup after transplantation or mean calculated creatinine clearance. Vesicoureteral reflux was found in 1 child with posterior urethral valves and 3 of the children in the control group (p not significant). A total of 15 urinary tract infections occurred in 5 children (36%) with posterior urethral valves, for a rate of 1 per 30 patient-months of followup, and 6 urinary tract infections occurred in 2 controls (7%), for a rate of 1 per 216 patient-months of followup (p < 0.05). However, only 1 of 26 controls (4%) without vesicoureteral reflux had urinary tract infection, for a rate 1 per 1,144 patient-months (p < 0.01). Conversely, the rate of urinary tract infections in controls with vesicoureteral reflux was similar to that of children with posterior urethral valves. Of the 5 children with posterior urethral valves 4 had the initial urinary tract infection within 2 months of transplantation and 10 of 15 episodes occurred within the first 4 months. Antimicrobial prophylaxis did not appear to decrease the rate of infection in children with posterior urethral valves. A history of posterior urethral valves increases the frequency of urinary tract infection after renal transplantation but the usefulness of antimicrobial prophylaxis and the relationship to long-term graft function remain to be determined. Urinary tract infection rarely develops in other transplanted boys without vesicoureteral reflux.

Adolescent↗
PubMed1992

Effect of recipient's race on pediatric renal allograft survival: a single-center study.

One hundred twenty-seven children (83 males, 44 females, 86 white, 41 nonwhite; mean age 12.1 years) who received 160 renal transplants between 1980 and 1989 were retrospectively studied. Variables such as age, sex, primary diagnosis, type, HLA-DR mismatching, and repeated transplants were compared between races and found not to be significant. However, HLA-A and -B cadaveric-graft mismatching, which was equivalent between whites and nonwhites prior to 1985 (pre-cyclosporine A era), has significantly favored whites (49% with 0 to 2 HLA-A and -B mismatch vs 16% in nonwhites) since 1985 (P less than .05), and a significantly higher proportion of nonwhite patients (59%) were receiving medical assistance (P less than .0001). Graft survival was evaluated with significantly poorer results in nonwhites as compared to whites (P less than .05). Although no difference was found between white and nonwhite cadaveric-graft survival before 1985, nonwhites had significantly worse graft survival since 1985 (72% vs 59% for 1 year and 61% vs 24% for 3 years in whites and nonwhites, respectively; P less than .05). Subpopulations such as nonwhite adolescents, nonwhite females, nonwhites with repeated transplants, and all low socioeconomic patients were identified as high-risk children with poor long-term survival. It is concluded that secondary to poorer matching since 1985 there has been decreased graft survival in nonwhites despite cyclosporine A. Attempts to improve matching and attention to high-risk groups are needed for equivalent survival.

Adolescent↗
PubMed1991

Combined liver-kidney transplantation in a child with primary hyperoxaluria.

A 3.5-year-old boy presented with end-stage renal disease and bilateral nephrocalcinosis. Renal biopsy demonstrated marked parenchymal calcium oxalate deposition and a diagnosis of primary hyperoxaluria (PH) was made. Following 2 years of hemodialysis he received two renal allografts which were lost at 7 and 11 months, respectively, due to biopsy-proven recurrent oxalosis. Combined liver-kidney transplantation was then performed, after which renal and hepatic function initially stabilized. The patient died on the 28th postoperative day, of infectious complications and progressive respiratory insufficiency. However, comparisons between the patterns of urinary oxalate excretion noted after the isolated renal and liver-kidney transplants indicated that, following the latter, successful biochemical correction of the enzyme defect responsible for type 1 PH had occurred.

Child, Preschool↗
PubMed1991

On the receiving end. IV: Validation of quality of life indicators.

Four measures of patient functioning and a mood adjective list currently used in trials of the International Breast Cancer Study Group (IBCSG), and an 8-item Linear Analogue Self Assessment (LASA) instrument measuring specific side effects of cancer and cancer treatment (GLQ-8), were cross-validated against three established measures of quality of life, mood and psychological adjustment to cancer, in a heterogeneous sample of cancer patients. Correlations between new and established measures were high, indicating good convergent and concurrent validity. Compliance on the longer mood measures was relatively poor. Despite the difficulty in developing direct and methodologically sound measures of quality of life, the regular inclusion of practical indicators of aspects of quality of life in clinical trials would allow improved assessment of the cost-benefit ratio of treatment to outcome in cancer patients.

Adaptation, Psychological↗
PubMed1990

Table-sag errors in CT treatment planning.

It is common practice to utilize CT scans in place of patient contours for computerized treatment planning. Our experience, in particular with pelvic patients, is that setting up the patient for a CT scan using landmarks from a radiation therapy simulator does not always produce accurate field margins. In general, the treatment field center as produced by the CT scan is superior to the center as defined by the simulator film. We have determined this problem to be caused by simulator table sag as compared to the CT. We offer suggestions to correct the problem.

Humans↗
PubMed1986

Identification of three sites of proteolytic cleavage in the hinge region between the two domains of the beta 2 subunit of tryptophan synthase of Escherichia coli or Salmonella typhimurium.

The beta 2 subunit of tryptophan synthase is composed of two independently folding domains connected by a hinge segment of the polypeptide that is particularly susceptible to limited proteolysis by trypsin [Högberg-Raibaud, A., & Goldberg, M. (1977) Biochemistry 16, 4014-4019]. Since tryptic cleavage in the hinge region inactivates the beta 2 subunit, the spatial relationship between the two domains is important for enzyme activity. However, it was not previously known whether inactivation results from cleavage of the chain or from the loss of internal fragment(s) subsequent to cleavage at two or more sites. We now report comparative studies of limited proteolysis by three proteinases: trypsin and endoproteinases Lys-C and Arg-C. Our key finding that endoproteinase Arg-C inactivates the beta 2 subunit by cleavage at a single site (Arg-275) demonstrates the important role of the hinge peptide for enzymatic activity. We have also identified the sites of cleavage and the time course of proteolysis by trypsin at Arg-275, Lys-283, and Lys-272 and by endoproteinase Lys-C at Lys-283 and Lys-272. Sodium dodecyl sulfate gel electrophoresis, Edman degradation, and carboxypeptidases B and Y have been used to identify the several fragments and peptides produced. Our finding that the beta 2 subunit and F1 fragments have a heterogeneous amino terminus (Met-1 or Thr-2) indicates that the amino-terminal methionine is incompletely removed during posttranslational modification. Our results show that Edman degradation can be effectively used with a protein of known sequence to analyze proteolytic digests that have at least four different amino-terminal sequences.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗
PubMed1979

Evaluation of a class III biological safety cabinet for enclosure of an ultracentrifuge.

An evaluation of a special safety cabinet housing a high-speed centrifuge was made. The cabinet enclosed both the top access port and the drive and pumping machinery of the centrifuge. A titanium rotor was loaded with tubes containing a bacterial culture, weakened, and driven until rotor rupture occurred. There were several bent and broken components in the centrifuge, and bacteria leaked from the vacuum chamber. Although the forces were sufficient to displace the cabinet, none of the test bacteria were found outside the cabinet.

Aerosols↗
PubMed1979

Extracellular fluid of the kidney preserved by the Collins technique.

Hilar drainage fluid of dog kidneys was analyzed as an approximation to renal extracellular fluid after preservation by flushing with chilled high K-low Na solution (Collins C4) followed by ice-cold storage for 24 and 48 hr in a bath of flushing medium. Compared with the medium, Na and Cl were increased to 30 mM/liter and K decreased slightly to 93 mM/liter. Glucose decreased, whereas lactate, lactic dehydrogenase, and creatine phosphokinase increased by significant amounts in both the drainage fluid and bath. The inulin space of the undrained kidney average 37% of wet weight. Calculated intracellular Na and Cl concentrations averaged 50 and 37 mM/kg cell water while K remained within normal limits. A significant fraction of red blood cells retained during initial flushing entered the effluent during storage. Bath and effluent composition of a human cadaver kidney approximated those of a dog.

Animals↗
PubMed1976

Cellular proliferation in the urinary tract epithelium of the rat following temporary unilateral renal ischaemia.

A study of the effect of temporary unilateral renal ischaemia on the epithelium lining the renal pelvis and the bladder of the rat is described. There is a significant increase in the mitotic index in the pelvic epithelium of the affected kidneys, presenting a well-defined peak approximately 36 h after reflow. A similar but less pronounced cellular proliferation occurs in the bladder epithelium. The increased mitotic index in the renal pelvis and the bladder is not preceded by any detectable cell destruction at either site. It also has a different time course from the tubular regeneration which follows renal ischaemia.

Animals↗
PubMedDate not supplied

The provision and evaluation of a neonatal resuscitation program.

The need to train perinatal staff in neonatal resuscitation is widely accepted; however, standardized educational programs have not been available. This study used a randomized control trial to evaluate a one-day neonatal resuscitation education program with 190 nurses. Experimental subjects receiving the program had significantly improved knowledge and skill performance. Knowledge, but not skill performance, was maintained at six months for the experimental group. There was a significant relationship between subjects' self-rating of knowledge and performance, suggesting that this method could be used to prioritize staff for basic or refresher training. An effective format and evaluation instruments for neonatal resuscitation training have been developed. Strategies to maintain skills should be addressed in future research.

Adult↗