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Biomedical subjects

D L Dunn

Publications and source records attributed to D L Dunn.

At least 235 records · Page 13Linked to original sources
PubMed1988

Protective capacity of polyclonal and monoclonal antibodies directed against endotoxin during experimental sepsis.

Both monoclonal antibody (MAb) and polyclonal antibody (PAb) directed against the shared core/lipid A region of lipopolysaccharide (LPS) (endotoxin) provide protection during experimental gram-negative bacterial sepsis. Although these preparations have not been compared, clinical trials administering either preparation to septic patients have been instituted. The core/lipid A region of LPS represents an antigenic domain common to many, if not all, gram-negative microbes, and thus represents an ideal target site for antibody binding. We sought to determine (1) the protective capacity of similarly reactive IgG anti-core LPS/lipid A MAbs and PAbs, (2) whether the timing of administration was important, and (3) whether either would act additively with antimicrobial agents. Antibody was administered intravenously to outbred mice, and Escherichia coli 0111:B4 was then administered intravenously or intraperitoneally with hemoglobin. Monoclonal antibodies and PAbs were equally protective, and protection was maximized by pretreatment, although the effect extended to four hours after bacterial challenge. Both MAbs and PAbs acted in concert with gentamicin hydrochloride to further reduce lethality. We concluded that MAbs and PAbs were equally protective and that clinical utility may eventually be dictated by ease and cost of antibody production.

Antibodies↗
PubMed1988

The role of intestinal flora on the interactions between nonparenchymal cells and hepatocytes in coculture.

Kupffer cells are exposed directly to a number of factors in the portal circulation that can modify or regulate their responses to septic stimuli. The gut represents a potential source of a number of these factors including endotoxin, lymphokines, and prostaglandins. We examined Kupffer cells from germfree rats and germfree rats exposed to endotoxin or bacteria via their GI tracts to determine the importance of the intestinal flora in maintaining or modulating Kupffer cell responses. Kupffer cells from germfree animals were reduced in numbers and failed to respond to LPS in Kupffer cell: hepatocyte coculture. When germfree rats were exposed to bacterial endotoxin or bacteria via the gastrointestinal tract their Kupffer cells increased in numbers to normal and the cells responded to LPS in culture. Intestinal overgrowth with Escherichia coli for 2 days activated the Kupffer cells and significantly increased Kupffer cell sensitivity to LPS. These data suggest that the environment of the gastrointestinal tract is important for normal Kupffer cell responses and that intestinal bacterial overgrowth can modify Kupffer cell responses to septic stimuli.

Animals↗
PubMed1988

Antibody immunotherapy of gram-negative bacterial sepsis in an immunosuppressed animal model.

Leukopenic, immunosuppressed recipients of solid organ allografts are at high risk for gram-negative bacterial sepsis, and mortality remains unacceptably high (greater than 30%). The purpose of this study was to determine whether murine monoclonal antibody (MAb) directed against lipopolysaccharide (LPS, endotoxin) would reduce lethality caused by a septic insult in immunosuppressed mice, and to determine if a specific antibody class would prove more efficacious in this setting. Two MAbs (3-H9, IgG3; 7-B5, IgM) were selected that reacted by ELISA, immunodot blot, and Western blot analysis against the O antigen polysaccharide portion of Escherichia coli 0111:B4 LPS. The 3-H9 MAb, 7B-5 MAb, or sterile saline was administered i.v. to normal or neutropenic Swiss-Webster mice immediately prior to an E coli 0111:B4 bacterial (i.v. or i.p. plus hemoglobin) or LPS (i.v.) challenge. In normal mice, administration of 3-H9 MAb or 7-B5 MAb i.v. immediately prior to a bacterial or endotoxin challenge resulted in a significant increase in the LD50. Neutropenia lowered the LD50 by nearly one log10 in both the bacteremia and peritonitis models. Both MAbs provided similar protection, raising the LD50 one log10 in neutropenic mice. Thus neutropenic animals receiving either MAb had a mortality nearly identical to that of normal animals receiving saline. No significant difference between the protective capacity of these MAbs was noted in any of the three models. These studies demonstrate that MAbs directed against LPS exert protection during gram-negative bacterial sepsis in either normal or neutropenic animals. In addition, the particular IgG and IgM MAbs examined provided similar protective capacity. Antibody directed against LPS may provide an additive form of therapy that may serve to decrease lethality during clinical gram-negative sepsis in immunosuppressed patients.

Animals↗
PubMed1988

Single-center 1-15-year results of renal transplantation in patients with systemic lupus erythematosus.

Initially, poor long-term prognosis in patients with SLE and fear of recurrent disease dissuaded renal transplantation in this group of patients. However, in 1975 the Advisory Committee to the Renal Transplant Registry reported satisfactory 1-2-year results in 56 patients with SLE from 36 institutions. Subsequently, renal transplantation for SLE patients with end-stage renal disease has become more accepted, though it has been recommended that transplantation be postponed for at least one year after initiating dialysis. Five cases of recurrent lupus nephritis have been reported in the literature. However, since the long-term outcome after transplantation in this group of patients is not well established, we have examined the long-term outcome in SLE patients who underwent renal transplantation at the University of Minnesota. Thirty-two SLE patients receiving 33 transplants between December 1969 and December 1987 were studied retrospectively and compared with controls matched for age, sex, donor source, HLA match, date of transplant, and diabetic status. A total of 69% (22/32) of patients underwent less than 1 year of dialysis prior to transplantation, and 50% (16/32) experienced biopsy-proved acute rejection, which was reversible in 67% (11/16). Actuarial graft function and patient survival rate in SLE patients were not significantly different from those in the matched control group. Duration of prior dialysis did not affect outcome. Surviving grafts have excellent function as measured by serum creatinine (1.3 +/- 0.4 mg/dl, means +/- SD). Causes of death were sepsis (5) and myocardial infarction (1). One patient lost the graft from rejection after withdrawal of immunosuppression because of a malignancy one month posttransplant. Three patients lost graft function due to chronic rejection. To date no patients have had evidence of recurrent SLE nephritis.

Follow-Up Studies↗
PubMed1988

Pancreas transplantation in nonuremic, type I diabetic recipients.

Between July 1978 and January 1988, 111 of 210 pancreas transplants were in nonuremic, nonkidney (NUNK) recipients in whom complications of diabetes were judged more serious than the potential side effects of antirejection therapy. In all NUNK cases, the 1-year patient survival rate (PSR) and graft survival rate (GSR) were 90% and 39%. Since November 1984, 1-year PSR and GSR for 62 NUNK recipients of pancreas transplants alone (PTA) were 93% and 48%, compared to 89% and 37% for 28 pancreas transplants after (PAK) and 89% and 73% for 20 simultaneous (SPK) with a kidney transplant. The 1-year GSR for 1984-88 technically successful (TS) PTA cases (n = 47) was 63%, versus 75% for PAK (n = 13) and 86% for SPK (n = 17) cases. The 1-year GSRs, by technique and source for 1984-88 PTA cases, were 58% for bladder-drained cadaver (n = 30), 51% for enteric-drained related (n = 32), and 29% for enteric-drained cadaver (n = 17) donor transplants, and 75% (n = 24), 77% (n = 16), and 38% (n = 13) for the corresponding TS cases. Of NUNK recipients, 35 have had grafts function for more than 1 year and all but 3 were treated with cyclosporine (CsA). In the CsA-treated recipients, serum creatinine increased and creatinine clearances decreased by a magnitude of 40% during the first 6 months but thereafter remained stable in all but 2 patients. In the patients with functioning grafts studied at 1 year, retinopathy remained stable in 59% and progressed in 41% of the eyes (n = 39). Motor nerve conduction velocities were significantly increased and muscle action potentials remained stable in 24 patients with functioning grafts studied at 1 year, while in 14 patients in whom transplants failed there was a significant decrease in evoked muscle action potentials. A sustained euglycemic, insulin-independent state can be established in nonuremic, nonkidney diabetic recipients of pancreas transplants alone, with a beneficial effect on neuropathy, lack of an immediate benefit on advanced retinopathy, and an effect on nephropathy compounded by the influence of CsA on renal function.

Cyclosporins↗
PubMed1987

Macrophages and translymphatic absorption represent the first line of host defense of the peritoneal cavity.

To quantitate the host defenses of the rat peritoneal cavity, nonviable radiolabeled Escherichia coli were injected intraperitoneally and clearance, leukocyte influx, and phagocytosis were examined. Macrophages (MCs) were present initially and remained relatively constant in number. The polymorphonuclear leukocyte (PMN) response began at one to two hours and was maximal at 24 to 72 hours. A previously unidentified inoculum-dependent PMN response was defined. Clearance and phagocytosis were extremely rapid, and few (less than 3%) free bacteria were present after two hours. Phagocytic activity of MCs and PMNs was identical, but MCs were numerically predominant initially and thus accounted for the majority of early phagocytosis. Thus, MC phagocytosis and clearance represent the primary line of host peritoneal defenses. We hypothesize that the subsequent inoculum-dependent PMN response may have evolved to cope with those larger inocula for which this initial response is inadequate.

Absorption↗
PubMed1987

Antibody immunotherapy of gram-negative bacterial sepsis.

Gram-negative bacterial sepsis continues to represent a significant cause of morbidity and mortality in hospitalized patients. Currently available medical therapy (antimicrobial agents, hemodynamic monitoring, aggressive fluid resuscitation, and nutritional support) for this disease process has reduced but not eliminated the severe consequences that may ensue. Recent investigations have demonstrated the ability of antibody directed against gram-negative bacterial lipopolysaccharide (LPS or endotoxin) to afford protection during experimental gram-negative bacillary sepsis. The core LPS-lipid A portion of endotoxin represents a determinant shared by many common gram-negative microorganisms that is luxuriantly expressed on the cell surface of rough mutants of Escherichia coli and Salmonella minnesota. These organisms or the outer membrane LPS isolated from them thus represent suitable immunogens for the development of cross-protective antibody preparations. Large quantities of highly cross-reactive antibody may potentially be obtained from several sources: murine or human monoclonal antibodies, immunization of large animals or humans with subsequent plasmapharesis and antibody isolation, affinity purification of large amounts of normal antibody, and pooling of prescreened lots of normal animal or human antibody that react to a particular bacterial antigen.

Antibodies, Bacterial↗
PubMed1987

Vaccines and antibody immunotherapy in surgical patients.

Immunoprophylaxis of infectious complications in surgical patients is currently practiced and is efficacious for disease caused by Clostridium tetani, rabies virus, Streptococcus pneumoniae, and hepatitis B virus. Evidence exists that immunoprophylaxis and treatment of herpes viruses as well as gram-negative pathogens is possible, although extensive clinical testing will be required to establish immunotherapy as a effective clinical treatment modality for the control of disease caused by these agents. Advances in our understanding of the host immune response and the ways in which it may be stimulated or supplemented should provide the means to further reduce the morbidity and mortality caused by a variety of pathogenic microbial agents.

Humans↗
PubMed1987

Isolation and characterization of murine monoclonal antibodies specific for gram-negative bacterial lipopolysaccharide: association of cross-genus reactivity with lipid A specificity.

Somatic cell hybrids secreting monoclonal antibodies against the core-glycolipid portion of enterobacterial endotoxin were derived from mice immunized with Escherichia coli J5 or Salmonella minnesota R595 heat-killed organisms or lipopolysaccharide (LPS). Eight antibodies were selected for their ability to cross-react with several members of a panel of gram-negative bacterial antigens in a radioimmunoassay. This panel represented five genera and two families of organisms: E. coli O111:B4, E. coli O55:B5, Klebsiella pneumoniae, Pseudomonas aeruginosa, Salmonella minnesota, and Serratia marcescens. The binding sites for six of the antibodies were unequivocally localized within the lipid A moiety of the endotoxin molecule by using the radioimmunoassay on LPS and free lipid A. The anti-lipid A antibodies were further characterized for their ability to interact with LPS variants by using a sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunostaining procedure. The monoclonal antibodies bound almost exclusively to the low-molecular-weight species of LPS on the polyacrylamide gel. These components corresponded to LPS isolated from rough strains of organisms (strains which lack O-specific carbohydrate). These results suggested that the cross-reactive component of antisera raised against rough mutants of gram-negative bacteria contain antibodies of lipid A specificity. Moreover, the determinant within the lipid A moiety of LPS may have been accessible to the monoclonal antibodies only in those endotoxin molecules on the outer membrane surface which lack the O-specific carbohydrate.

Animals↗
PubMed1987

The impact of DRG payment on New Jersey hospitals.

Debate persists about the most effective way to pay hospitals to limit health care cost inflation. New Jersey, the first state to adopt the DRG payment system, has accumulated sufficient experience to allow a comparison of the relative efficacy of two reimbursement methods. Regression results, using a time trend specification, indicate that per case payment based on diagnosis related groups was no more successful in controlling hospital costs per capita than a previous per diem payment system. There were, however, significant changes in costs per case and length of stay. But the increase in admission rates neutralized the reduction in costs per case. There were no significant overall cost savings.

Diagnosis-Related Groups↗
PubMed1987

Economic incentives and organizational realities: managing hospitals under DRGs.

Diagnosis-related Groups (DRGs) offer hospitals financial incentives to improve efficiency. To be effective, DRGs require a realignment of management so that physicians' use of resources can be disciplined by administrators. The constituency for altering power relationships within hospitals, however, is, at best, a weak one: administrators see their primary task as the protection of physicians' clinical autonomy. Constraints imposed on hospitals by regulators can be accommodated by minor adjustments in behavior that ensure neither gains in efficiency nor changes in decision-making authority.

Accounting↗
PubMed1986

Immunotherapy of gram-negative bacterial sepsis. A single murine monoclonal antibody provides cross-genera protection.

Previous experimental and clinical studies have demonstrated the ability of polyclonal antibody directed against the core lipopolysaccharide (LPS)-lipid A component of endotoxin to reduce mortality. We sought to characterize the ability of a single murine monoclonal IgG1 antibody (8A1 MAb) to react to a variety of gram-negative microorganisms, to promote phagocytosis, and to provide protection during experimental murine sepsis. The 8A1 MAb reacted to various gram-negative bacterial whole cell and LPS antigens examined by enzyme-linked immunosorbent assay. Reactivity was highest to Salmonella minnesota Re LPS and lipid A. Phagocytosis was promoted by this monoclonal antibody to several gram-negative bacteria, except Pseudomonas aeruginosa. The 8A1 MAb (2 mg per mouse) enhanced survival during bacteremia due to either Escherichia coli 0111:B4 or Klebsiella pneumoniae, and during endotoxemia due to all types of LPS examined except P aeruginosa. We concluded that a single MAb with anti-lipid A specificity was cross reactive in vitro and cross protective in vivo. A clinical trial comparing polyclonal and monoclonal antibody in high-risk septic patients seems warranted.

Animals↗