Donald L. Kreutzer

University of Connecticut

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Role of bacterial phospholipases in serum-mediated killing of Escherichia coli

Infection and Immunity (1977)

Donald L. Kreutzer M Vandermaten C. S. Buller D C Robertson AKEMI HIRATA

The importance of bacterial phospholipases during serum-mediated killing of Escherichia coli was examined by using wild-type DR+ DS+ and an isogenic phospholipase-deficient mutant DR- DS-. No difference in serum sensitivity was observed when the parental DR+ DS+ and mutant DR- DS- strains were exposed to various concentrations of normal guinea pig serum. Examination of the free fatty acid (FFA) and lipid composition during serum-mediated killing of the two E. coli strains indicated that FFA release occurred only in the parental DR+ DS+ strain. No FFA release or lipid degradation was detected in the mutant DR- DS- strain during serum killing. The addition of heat-inactivated E. coli antiserum (rabbit) to normal guinea pig serum caused FFA release in both E. coli strains. This FFA release was found to be independent of serum-mediated killing and due to a highly active and heat-resistant rabbit serum phospholipase that hydrolyzed the bacterial lipids after serum killing. The data presented indicate that serum-mediated killing of E. coli is independent of FFA release and that activation of bacterial phospholipases and the resulting release of FFA are only a result rather than a cause of serum-mediated cell death.

Phospholipase A

10.1128/iai.18.1.183-188.1977

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Citations (5)

Cytokine expression by head and neck squamous cell carcinomas

The American Journal of Surgery (1992)

Eric Mann Jeffrey D. Spiro Lei L. Chen Donald L. Kreutzer

Interleukin 20

10.1016/s0002-9610(05)80708-1

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Citations (99)

Basement Membrane-Based Glucose Sensor Coatings Enhance Continuous Glucose Monitoring in Vivo

Journal of Diabetes Science and Technology (2015)

Ulrike Klueh Yi Qiao Caroline Czajkowski Izabela Ludzinska Omar Antar

Implantable glucose sensors demonstrate a rapid decline in function that is likely due to biofouling of the sensor. Previous efforts directed at overcoming this issue has generally focused on the use of synthetic polymer coatings, with little apparent effect in vivo, clearly a novel approach is required. We believe that the key to extending sensor life span in vivo is the development of biocompatible basement membrane (BM) based bio-hydrogels as coatings for glucose sensors.BM based bio-hydrogel sensor coatings were developed using purified BM preparations (ie, Cultrex from Trevigen Inc). Modified Abbott sensors were coated with Cultrex BM extracts. Sensor performance was evaluated for the impact of these coatings in vitro and in vivo in a continuous glucose monitoring (CGM) mouse model. In vivo sensor function was assessed over a 28-day time period expressed as mean absolute relative difference (MARD) values. Tissue reactivity of both Cultrex coated and uncoated glucose sensors was evaluated at 7, 14, 21 and 28 days post-sensor implantation with standard histological techniques.The data demonstrate that Cultrex-based sensor coatings had no effect on glucose sensor function in vitro. In vivo glucose sensor performance was enhanced following BM coating as determined by MARD analysis, particularly in weeks 2 and 3. In vivo studies also demonstrated that Cultrex coatings significantly decreased sensor-induced tissue reactions at the sensor implantation sites.Basement-membrane-based sensor coatings enhance glucose sensor function in vivo, by minimizing or preventing sensor-induced tissues reactions.

10.1177/1932296815598776

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Citations (12)

Selective neutrophil desensitization to chemotactic factors.

The Journal of Cell Biology (1979)

Joseph T. O’Flaherty Donald L. Kreutzer Henry J. Showell G. Vitkauskas Elmer L. Becker

In the presence of extracellular calcium and magnesium, a series of chemotactic oligopeptides and C5a caused aggregation of human polymorphonuclear neutrophils (PMNs). This cellular response developed rapidly and began to reverse 2 min after exposure to the chemotactin. In the absence of the bivalent cations, none of the chemotactins stimulated the aggregation response. If cells were first exposed to a chemotactin and then treated with calcium and magnesium, aggregation was detected only after addition of the cations, and the magnitude of the response fell sharply as the interval between the addition of chemotactin and addition of cations was lengthened: when this interval exceeded 2 min, aggregation was barely detectable. This loss of reactivity persisted even when cells were re-exposed to fresh chemotactic factor and washed between the first and second exposures. In all instances, however, loss of cellular reactivity was highly selective: cells preincubated with any chemotactic oligopeptide were hyporesponsive to subsequent stimulation with an oligopeptide but remained fully responsive to C5a; cells preincubated with C5A were hyporesponsive to C5a but retained their responsitivity to the oligopeptides. Because this selectivity parallels the known specificities of these chemotactic factors for their receptors in or on the neutrophil, desensitization may reflect functional loss of receptors after stimulation. Alternatively, this selectivity may indicate that morphologically identical neutrophils contain subpopulations of cells with varying reactivities to receptor-bound chemotactic factors. In either event, desensitization may be useful in functionally defining chemotactic factors and their respective receptors. The rapidity of development of desensitization suggests that it may operate to limit or moderate various in vitro and in vivo neutrophil responses to chemotactic factors.

Oligopeptide

N-Formylmethionine leucyl-phenylalanine

10.1083/jcb.80.3.564

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Citations (88)

Fibrin induction of tissue plasminogen activator expression in corneal endothelial cells in vitro.

PubMed (1993)

Melinda L. Ramsby Donald L. Kreutzer

Fibrin is deposited in the anterior chamber of the eye in response to injury and can damage corneal endothelial cells (CEC). Fibrin degradation is plasmin dependent and is regulated by the balance between plasminogen activators (PA), tissue-PA (t-PA), urokinase-PA (u-PA), and their inhibitors (PAI). Although several factors can modulate PA/PAI expression in cells, the effect of fibrin is inconclusive. We hypothesized that fibrin can regulate fibrinolysis in the anterior segment by modulating PA/PAI expression in CEC.Bovine CEC (BCEC) were treated for 3 to 72 hours with in situ polymerized fibrin (2 mg/ml) +/- 35S-methionine, cycloheximide, or actinomycin D. Polymerization was thrombin catalyzed, and control BCEC were incubated with or without thrombin or polymerization by-products. PA and PAI in conditioned medium, fibrin matrix, and cell fractions were analyzed by PA-specific zymographic and enzymatic assays.Fibrin treatment induced a dramatic (> 20-fold) accumulation of extracellular, fibrin-bound PA. This activity was identified as t-PA by its Mw (70 kD) affinity for fibrin and sensitivity to inhibition by Erythrina. Induction of t-PA was not observed in control BCEC under any condition. Fibrin induction of t-PA was selective because the levels of u-PA (45 kD), PAI-1 (50 kD), or protein synthesis in general were unaffected. Fibrin induction of t-PA was not accompanied by changes in cellular t-PA levels and was dependent on both RNA and protein synthesis.Fibrin selectively induces t-PA expression in CEC. Induced t-PA is released extracellularly and binds exclusively to the fibrin matrix. These findings suggest a role for fibrin and CEC in the regulation of fibrinolysis in the anterior segment of the eye.

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Citations (32)

Mechanisms of Inflammation in Lung Tissue

Advances in experimental medicine and biology (1981)

Donald L. Kreutzer Usha Desai W.H. Douglas Mark E. Blazka

10.1007/978-1-4757-0495-2_21

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Citations (1)

Fibrin induction of thrombospondin in corneal endothelial cells in vitro.

PubMed (1993)

Melinda L. Ramsby Donald L. Kreutzer

Fibrin deposition in the anterior chamber of the eye occurs in response to injury or inflammation and can permanently damage the corneal endothelium. Fibrin functions as a mediator of inflammation and wound healing by affecting cell morphology and function in a variety of cells, including corneal endothelial cells. We hypothesized that fibrin can directly induce corneal endothelial cells to express injury-related proteins (eg, thrombospondin [TSP]) necessary for corneal repair processes.Bovine corneal endothelial cells (BCECs) were pulse- or continuously labeled with 35S-methionine in the presence or absence of in situ polymerized fibrin (2 mg/ml). BCECs were harvested after 3-48 hr, and 35S-labeled proteins were analyzed by SDS-PAGE, autoradiography, and immunochemical techniques.Fibrin selectively induced BCECs to express a high molecular weight (MW) protein that was present extracellularly in conditioned medium and fibrin matrix. This induction represented a 3-5 fold increase relative to nonfibrin-treated BCECs, was not accompanied by corresponding changes in 35S-labeled intracellular proteins, and was evident at early (3 hr) or late times (24 hr) post-fibrin treatment. The induced protein had an apparent MW of 180 kD (reduced) and > 420 kD (nonreduced), consistent with the characteristics of TSP. A polyclonal antibody to human TSP recognized the reduced form (180 kD) on Western blots and the native form (> 420 kD) in immunoprecipitation studies.Fibrin induces BCECs to express TSP, a matrix protein involved in cell-cell and cell-matrix interactions and implicated in wound healing.

Thrombospondin 1

Corneal Endothelium

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Citations (13)

Cytokines stimulate lipid membrane peroxidation of human sperm

Fertility and Sterility (1994)

Jeffrey P. Buch Thomas F. Kolon Nilanjana Maulik Donald L. Kreutzer Dipak K. Das

Proinflammatory cytokine

10.1016/s0015-0282(16)56838-1

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Citations (90)