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J R Bender

Publications and source records attributed to J R Bender.

At least 19 recordsLinked to original sources
PubMed1995

Conserved regions in the cytoplasmic domains of the leukocyte integrin alpha L beta 2 are involved in endoplasmic reticulum retention, dimerization, and cytoskeletal association.

Selected functions of integrins, including regulated cytoskeletal association and transmembrane signaling, depend on a poorly defined bidirectional communication between the extracellular and cytoplasmic domains of the alpha and beta subunits. To investigate this problem in the leukocyte integrin alpha L beta 2 (LFA-1), we generated a series of cytoplasmic truncation or internal substitution mutants of the alpha L and beta 2 cytoplasmic domains, and assessed their biochemical and functional properties upon ectopic expression in constitutively adherent cells. Expression of the alpha L beta 2 heterodimer in stably adherent cells is sufficient to promote its constitutive cytoskeletal association. Structural determinants for such association are located in selected regions of the beta 2 cytoplasmic domain, which display functional interdependence. In addition, a conserved region (Arg733-Lys742) in the beta 2 cytoplasmic domain seems to be critical not only for its cytoskeletal association, but also for endoplasmic reticulum retention, assembly, and transport to the plasma membrane of the mature alpha L beta 2 heterodimer. Analysis of deletion mutants of the alpha L subunit demonstrates a role of the conserved, membrane-proximal GFFKR motif in conferring stability to the alpha beta complex, possibly because of its direct involvement in heterodimer formation. We propose that a previously uncharacterized association of defined subregions of the cytoplasmic domains of integrin alpha and beta subunits affects the dimerization and regulated function of the adhesion receptor.

Allosteric Regulation↗
PubMed1995

Contact-dependent endothelial class II HLA gene activation induced by NK cells is mediated by IFN-gamma-dependent and -independent mechanisms.

NK lymphocytes adhere avidly to allogeneic endothelial cells (ECs) and induce their membrane expression of MHC class II Ags in vitro. Endothelial class II expression augments EC-driven CD4+ T cell proliferation in vitro, and may amplify T cell recruitment and clonal expansion in vivo. Using an ex vivo lymphocyte-skin organ coculture model, NK cells could be found lining and inducing class II HLA on microvessel endothelium. Using neutralizing anti-IFN-gamma and anti-IFN-gamma receptor Abs, a spectrum of IFN-gamma dependence was observed for NK-mediated EC HLA-DR induction at the membrane and transcriptional levels, from negligible to moderate. Trans-well experiments displayed that direct NK-EC contact is required, and Ab inhibition studies indicated that the beta 2 integrin-ICAM-1 pathway(s) is critical in the generation of these responses. The use of HLA-DR alpha promoter constructs in transient transfection assays demonstrated that the highly conserved X and S transcription boxes are required in both IFN-gamma- and NK-mediated gene activation. As expected, because of the receptor species specificity, human IFN-gamma did not induce HLA-DR alpha promoter constructs transfected in Chinese hamster ovary cells, whereas NK cells did. Taken together, these results indicate that human allogeneic NK lymphocytes induce EC class II HLA gene activation and membrane expression in an adhesion-dependent, IFN-gamma-independent fashion and suggest that, in concert with any IFN-gamma-dependent component, this induction could represent an efficient mode of endothelial activation and immune amplification in vivo.

Antigens, Differentiation, B-Lymphocyte↗
PubMed1995

Lymphocyte adhesion-dependent calcium signaling in human endothelial cells.

Vascular endothelial cells (ECs) can undergo dramatic phenotypic and functional alterations in response to humoral and cellular stimuli. These changes promote endothelial participation in the inflammatory response through active recruitment of immune effector cells, increased vascular permeability, and alteration in vascular tone. In an attempt to define early events in lymphocyte-mediated EC signaling, we investigated cytosolic-free calcium (Ca2+) changes in single, Fluo-3-labeled human umbilical vein ECs (HUVECs), using an ACAS interactive laser cytometer. Of all lymphocyte subsets tested, allogeneic CD3-, CD56+ natural killer (NK) cells uniquely elicited oscillatory EC Ca2+ signals in cytokine (interleukin [IL]-1- or tumor necrosis factor [TNF])-treated ECs. The induction of these signals required avid intercellular adhesion, consisted of both Ca2+ mobilization and extracellular influx, and was associated with EC inositol phosphate (IP) generation. Simultaneous recording of NK and EC Ca2+ signals using two-color fluorescence detection revealed that, upon adhesion, NK cells flux prior to EC. Lymphocyte Ca2+ buffering with 1,2-bis-5-methyl-amino-phenoxylethane-N,N,N'-tetra-acetoxymethyl acetate (MAPTAM) demonstrated that lymphocyte fluxes are, in fact, prerequisites for the adhesion-dependent EC signals. mAb studies indicate that the beta 2 integrin-intercellular adhesion molecule (ICAM)-1 adhesion pathway is critically involved. However, ICAM-1 antisense oligonucleotide inhibition of IL-1-mediated ICAM-1 hyperinduction had no effect on EC Ca2+ signaling in lymphocyte-EC conjugates, indicating that additional cytokine-induced EC alteration is required. These experiments combine features of lymphocyte-endothelial interactions, intercellular adhesion, EC cytokine activation and transmembrane signaling. The results implicate the IP/Ca2+ second messenger pathway in EC outside-in signaling induced by cytotoxic lymphocytes, and suggest that these signals may play a role in EC alteration by lymphocyte adhesion.

Base Sequence↗
PubMed1994

Heterogeneous activation thresholds to cytokines in genetically distinct endothelial cells: evidence for diverse transcriptional responses.

It is well accepted that the induction of endothelial cell (EC) adhesion molecules is a critical component in acute inflammatory responses as well as allogeneic interactions in vascularized allografts and, possibly, atherogenesis. The "inflammatory triad" of interleukin 1 (IL-1), tumor necrosis factor, and lipopolysaccharide are potent stimulators of the EC activation/adhesion molecules intercellular adhesion molecule 1 (ICAM-1), endothelial-leukocyte adhesion molecule 1 (ELAM-1), and vascular cell adhesion molecule 1 (VCAM-1). To address whether there exist differing thresholds to cytokine-mediated EC activation, we utilized a panel of genetically distinct human umbilical vein EC lines, assessing their modulated EC surface expression and transcriptional responses to cytokines, with regard to the cell adhesion molecules (CAMs) ELAM-1, ICAM-1, and VCAM-1. With submaximal concentrations of cytokine, EC ELAM-1 surface expression varied from negligible to marked. This phenotypic response was maintained over numerous passages in culture and was observed in ex vivo organ culture analyses with cytokine-treated umbilical vein sections. Relative patterns of ELAM-1, ICAM-1, and VCAM-1 induction were similar in response to multiple stimuli (IL-1, tumor necrosis factor, and lipopolysaccharide, but not phorbol 12-myristate 13-acetate). Nuclear run-off experiments demonstrated that the "high responder" phenotype is a consequence of enhanced transcriptional activation of the CAM genes in response to IL-1 (1 unit/ml), whereas transcriptional responses in "low responders" are minimal. Despite the known involvement of NF-kappa B in endothelial CAM transcription, gel shift assays failed to demonstrate a correlation between the levels of IL-1-mediated nuclear NF-kappa B expression and CAM induction in high and low responding lines. We postulate that varying EC activation thresholds to cytokines observed here, in vitro, may be a critical determinant in the susceptibility to vasculopathic states.

Base Sequence↗
PubMed1994

Epican, a heparan/chondroitin sulfate proteoglycan form of CD44, mediates cell-cell adhesion.

Epican is a heparan/chondroitin sulfate proteoglycan form of CD44 and is expressed on the surface of keratinocytes from the basal layer to the granular layer of the epidermis. To analyze the adhesive properties of epican apart from the influence of other adhesive molecules found on keratinocytes, mouse L cell fibroblasts were transfected with CD44Epican cDNA. The epican expressed on the surface of transfected L cells was predominantly a heparan or chondroitin sulfate proteoglycan. The CD44Epican-transfected L cells acquired: (a) a self-aggregating phenotype that required hyaluronan but was calcium-independent; and (b) a new capacity to adhere to keratinocytes, a property that was blocked by an anti-epican antibody. Both aggregation and adhesion of CD44Epican-transfected cells were completely prevented by pretreatment with hyaluronidase, but were totally restored by the addition of exogenous hyaluronan. Aggregation of transfected L cells was minimally influenced by other glycosaminoglycans, but adhesion of transfected L cells to keratinocytes was substantially inhibited by heparin.

Animals↗
PubMed1994

Glass fiber manufacturing and fiber safety: the producer's perspective.

Historically, the potential health effects of airborne fibers have been associated with the dose, dimension, and durability. Increasing focus is being placed on the latter category. Concern about airborne fiber safety could be reduced by manufacturing fibers that are not respirable; however, due to performance and manufacturing constraints on glasswool insulations, this is not possible today. These products are an important part of today's economy and as a major manufacturer, Owens-Corning is committed to producing and marketing materials that are both safe and effective in their intended use. To this end, manufacturing technology seeks to produce materials that generate low concentrations of airborne fibers, thus minimizing exposure and irritation. The range of fiber diameters is controlled to assure effective product performance and, as far as possible, to minimize respirability. Glass compositions are designed to allow effective fiber forming and ultimate product function. Fiber dissolution is primarily a function of composition; this too, can be controlled within certain constraints. Coupled with these broad parameters is an extensive product stewardship program to assure the safety of these materials. This article will discuss the factors that influence glasswool insulation production, use, and safety.

Air Pollutants↗
PubMed1994

Science, public policy, and stewardship.

Synthetic vitreous fibers play an important role in today's economy. Glass fibers, as an example, have found uses in more than 30,000 products that include insulations, reinforcements, fire resistant fabrics, and protective armor. Vitreous fibers also play a direct role in energy conservation. For example, in 1992, a study by Arthur D. Little found that the annual production of fiber glass batts and blowing wool used in U.S. buildings--only a fraction of the current production and use of glass wool--saved the equivalent of 33.4 million barrels of oil in 1992, avoiding the need for nearly 6800 megawatts of power. This is equivalent to 34 new 200-megawatt power plants. An ongoing commitment by the manufacturers to assure the safety of their products paralleled the growth of the vitreous fiber industry. Soon after commercialization of glass wool manufacturing in the mid-1930s, worker concerns about silica gave rise to the first study on the health of fiber glass workers (Siebert, 1942). Since that time, there have been hundreds of studies, published papers, and international reviews that have evaluated potential health effects and exposures associated with synthetic vitreous fibers.

Air Pollutants, Occupational↗
PubMed1994

Measurement of respirable glass and total fiber concentrations in the ambient air around a fiberglass wool manufacturing facility and a rural area.

Little data are available on ambient concentrations of glass fibers which along with other manmade vitreous fibers are receiving increased regulatory attention. The purpose of this study was to measure glass and total respirable fibers around a large fiberglass wool manufacturing plant and a rural area. Samples were collected on mixed esters of cellulose filters using high-volume air samplers at flow rates of 1.2 m3/min. Fibers were counted using a modified NIOSH 7400B procedure. Glass fibers were found in very low concentrations for both areas sampled; 90% of the samples were below the detectable limit of 0.00001 fibers/cc. Average glass fiber concentrations accounted for less than 1% of the total fibers measured. Dispersion modeling was used to estimate ambient glass fiber concentrations around the plant. Predicted and measured results showed relatively good agreement.

Air Pollutants, Occupational↗
PubMed1993

Heterogeneity of dermal microvascular endothelial cell antigen expression and cytokine responsiveness in situ and in cell culture.

Microvascular endothelial cells (EC) recruit circulating leukocytes at sites of inflammation, in part through cytokine-regulated expression of endothelial-leukocyte adhesion molecules. Adhesion molecule expression varies among vascular beds and among EC within microvessels of a particular vascular bed. In the present study, we have examined the patterns of antigen expression and cytokine responsiveness of dermal microvascular endothelial cells (DMEC) in a skin organ culture model and, for comparison, in cell culture. Within the superficial vascular plexus (SVP) of normal skin, CD36 molecule expression is undetectable on capillary loops and is expressed on DMEC in only 20% of the larger, horizontal vessels. CD36 expression is not modulated by cytokines. Endothelial-leukocyte adhesion molecule-1 (ELAM-1) expression induced at 6 and 24 h by TNF or IL-1, is restricted to the venular side of the capillary loop and to the venules proper. Vascular cell adhesion molecule-1 (VCAM-1) expression is not inducible on EC of the SVP in normal skin by TNF, IL-1, or IL-4, alone or in combination at either time point. When inflamed skin is examined in organ culture, SVP EC are cytokine responsive regarding VCAM-1 expression. Within the deep vascular plexus (DVP). CD36 molecules are expressed on EC in all capillaries and small vessels. Both ELAM-1 and, to a lesser extent, VCAM-1 expression are inducible by TNF, IL-1, and/or IL-4 on capillaries and larger microvessels at 6 and 24 h. The larger vessels at the dermal-subcutaneous border were found to be CD36-/ELAM-1+/VCAM-1+ after cytokine treatment. CD36 expression of DMEC in cell culture varies from 47 to 98% of cells (mean 75%) in seven separate isolates and is not modified by cytokines. Upon TNF or IL-1 activation, 50 to 90% of DMEC express ELAM-1 molecules at 6 h and expression persists at high levels for 24 h. VCAM-1 expression is negligible at both times. These results with DMEC differ from human umbilical vein EC analyzed in parallel, which are completely CD36- and show transient ELAM-1 and sustained VCAM-1 expression in response to TNF and IL-1. In summary, we have demonstrated that DMEC comprise a heterogeneous population that differ from umbilical vein EC.

Animals↗
PubMed1993

Recent studies of man-made vitreous fibers. Chronic animal inhalation studies.

The history of asbestos use and asbestos-related disease is replete with comments that the public health would have been better protected if the results of laboratory investigation, epidemiologic surveys, and clinical studies were made available at appropriate intervals during the ongoing research, rather than in the generally accepted method of awaiting completion of studies prior to reporting medical and scientific findings. No substantive evidence of long-term adverse effects has been published in workers exposed to man-made vitreous fibers. Nevertheless, in an effort to preclude a repetition of this error of omission that occurred with asbestos exposure and use, the Thermal Insulation Manufacturers Association is regularly reporting interim and final data from ongoing animal studies. A significant segment of man-made vitreous fibers have now been tested in state-of-the-art chronic studies. This paper includes the recently completed animal inhalation studies on refractory ceramic fibers and fibrous glass. It also reviews interim data on mineral wool studies.

Air Pollutants, Occupational↗
PubMed1992

Early recognition of a discordant xenogeneic organ by human circulating lymphocytes.

Cell-mediated immune mechanisms underlying discordant xenograft rejection are poorly characterized. In our study, using a human to rat xenogeneic ex vivo model, we show that a fraction of human lymphocytes, when perfused through the coronary system of a rat heart, rapidly and specifically adheres to the vascular endothelium and infiltrates the myocardium. Lymphocyte phenotypic analysis before and after perfusion, as well as the use of purified cell subpopulations, demonstrate preferential adhesion of CD3- CD16+ NK cells. NK cell adhesion occurs via xenoreactive antibody-dependent and -independent pathways, because the selective removal of human IgG from the perfusion buffer markedly reduces but does not completely abrogate NK cell sequestration. However, T lymphocytes are retained in the xenoorgan via an antibody-independent pathway, as assessed by the lack of influence of IgG removal. Leukocyte integrins appear to play a crucial role in mediating adhesion of both lymphocyte subsets, because the pretreatment of lymphocytes with anti-CD11a, anti-CD11b, and anti-CD18 antibodies markedly reduces their retention into the xenogeneic organ. Retained human lymphocytes mediate rapid and direct damage of the xenoorgan, as demonstrated by histologic and functional alterations of the endothelium, impaired vascular resistance and in vitro lysis of rat endothelial cells by human NK cells. Taken together, these findings suggest a role for cell-mediated mechanisms in the rapid recognition and rejection of vascularized xenografts.

Animals↗
PubMed1992

Regulatory mechanisms in leukocyte adhesion: flexible receptors for sophisticated travelers.

Unstimulated leukocytes spend extended periods circulating in the blood, punctuated by migration through lymphoid areas and peripheral tissues. During transit, strong cell-cell interactions control immune surveillance and specialized effector functions. The structures and mechanisms that allow this flexible adhesion and migration behavior are the subject of this review.

Allosteric Regulation↗
PubMed1992

Antigen-receptor complex stimulation triggers protein kinase C-dependent CD11a/CD18-cytoskeleton association in T lymphocytes.

Although it is well accepted that intercellular adhesion involving the CD11a/CD18 (LFA-1) complex is critical in a wide array of T cell-dependent processes, recent demonstrations of an LFA-1 high avidity state, induced by triggering the T cell receptor (TCR) complex, has raised questions about the intracellular signals generated and molecular events leading to effective cell coupling, as well as their orderly sequence. In this study, we assessed the effects of T cell activation on the actin-based cytoskeleton, and LFA-1, as well as their interaction. Crosslinking the TCR complex with anti-CD3 mAb resulted in actin polymerization and colocalization with LFA-1, as detected by fluorescence microscopy. This association was confirmed by immunoprecipitating LFA-1 from the detergent insoluble, cytoskeletal-associated membrane fraction after TCR crosslinking. These consequences were inhibited by the protein kinase C (PKC) inhibitor staurosporine or by PKC desensitization, as was a transient CD11a hyperphosphorylation, induced by monoclonal anti-CD3. Furthermore, a small percentage of beta 2-deficient T cells maintained the ability to rearrange the cytoskeleton in response to TCR complex activation, with F-actin-VLA4 colocalization. These results provide evidence that the important consequences of TCR-induced signal transduction include a PKC-dependent cytoskeletal rearrangement, involving an association between leukocyte integrins and F-actin. We discuss the implications of these findings with respect to effective T cell functions.

Actins↗