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Biomedical subjects

B M Gebhardt

Publications and source records attributed to B M Gebhardt.

At least 55 records · Page 3Linked to original sources
PubMed1994

Central alpha-adrenergic involvement in morphine-mediated suppression of splenic natural killer activity.

Alpha 1-adrenergic pathways are involved in morphine-induced suppression of murine splenic NK activity. To investigate the level of involvement following morphine administration, the peripheral acting alpha-adrenoceptor antagonist doxazosin and the broad acting alpha-adrenoceptor antagonist phentolamine were employed. Mice preadministered phentolamine (2.0 mg/kg) exhibited a modest but insignificant suppression of splenic NK activity following morphine administration while mice preadministered doxazosin (1.0 mg/kg) or vehicle showed a significant decrease in splenic NK activity following morphine administration. Morphine was also found to significantly (P < 0.01) increase splenic serotonin levels (14.88 +/- 1.62 ng/mg) relative to saline-treated controls (7.3 +/- 0.9 ng/mg). Both phentolamine and doxazosin pretreatment completely or partially blocked morphine-mediated elevation of splenic serotonin levels, respectively. Morphine administration decreased the ability of NK cells to form conjugates with target (YAC-1 lymphoma) cells and decreased the number of active killer cells within the conjugate population. Collectively, these results implicate central alpha-adrenergic involvement following acute morphine administration in suppressing splenic NK activity indirectly through a reduction in the number of effector-target conjugates and active cytolytic effector cells.

Animals↗
PubMed1994

Collagen-based drug delivery and artificial tears.

For patients with conditions requiring chronic rather than acute therapy, the advantages of collagen shields in providing high and sustained levels of drugs and/or lubricants to the cornea are outweighed by the difficulty of insertion of the shield and the problem of blurred vision. We have developed a delivery system in which collagen pieces suspended in a viscous vehicle can be instilled into the lower forniceal space, thereby simplifying application and reducing blurring of vision. The collagen pieces (Collasomes) can be formulated with various constituents such as antibiotics or cyclosporine, or with chemical alterations such as the inclusion of a lipid (Lacrisomes) for the treatment of dry eyes. In the normal eyes of volunteers, Collasomes hydrated in a solution of sodium fluorescein and suspended in a methylcellulose vehicle as a model for delivery of water-soluble drugs produced fluorescein concentrations 17 to 42 times higher in the cornea and 6 to 8 times higher in the aqueous humor, compared with fluorescein-containing vehicle alone. In a preliminary controlled study, 76% of patients with moderately severe keratoconjunctivitis sicca (KCS) preferred Lacrisomes to the vehicle control because of a more soothing effect and longer duration of comfort. All preparations were well tolerated by all study subjects. Current studies involve improving drug delivery by chemically modifying the collagen molecule to slow diffusion of the drug from the Collasome matrix, as well as varying the amount of cetyl alcohol and combining it with modified collagen in Lacrisomes to maximize comfort in patients with dry eyes.

Adult↗
PubMed1994

A platelet-activating factor antagonist reduces corneal allograft inflammation and neovascularization.

We assessed the role of platelet-activating factor (PAF) in corneal allograft rejection and evaluated the effects of a PAF antagonist on corneal inflammation, cellular infiltration, vascularization, and edema. Rabbits with vascularized corneas served as recipients of allogeneic cornea grafts. Rabbits with normal corneas underwent autografts as controls. All of the allografts developed the progression of signs characteristic of rejection. Nevertheless, treatment with the PAF antagonist BN52021 significantly inhibited corneal allograft vascularization for up to 10 days after transplantation and reduced the number of eosinophils in the allografts at 28 days after transplantation. In contrast, saline-treated allografts exhibited florid vascularization and intense inflammatory infiltrates. Control autografts survived without developing significant inflammation or vascularization. The retardation of allograft eosinophilia and graft vascularization by the PAF antagonist was most likely the result of suppression of PAF-mediated reactions in the cornea. These results indicate that PAF may play a role in corneal inflammation and vascularization after corneal transplantation, and that PAF antagonists may be clinically useful in delaying some of the pathophysiologic consequences of corneal graft rejection.

Animals↗
PubMed1994

[An experimental study on cultivation of human trigeminal ganglionic cell in vitro and its sensitivity to infection of herpes simplex virus type 1].

We firstly report an experimental study on the sensitivity of primary cultural human trigeminal ganglionic cells infected by herpes simplex virus type 1 (HSV-1) in different time-points. The results indicate that the neuron of human trigeminal ganglia is the most sensitive cell type, the antigen of HSV-1 replicates rapidly within the cytoplasm and cell nucleus, the fibroblasts and glia cells are infected partly by the virus. Therefore, perhaps the neuron is the main harboring cell type.

Antigens, Viral↗
PubMed1993

Mitogen-stimulated lymphocytes release biologically active corticotropin.

We demonstrate that mitogen-activated lymphocytes release a biologically active form of ACTH that stimulates the in vitro release of corticosterone from cocultured rat adrenal cells. Neither nonstimulated lymphocytes nor the addition of mitogens alone to adrenal cell cultures had an effect. The steroidogenic activity could be neutralized by rabbit anti-ACTH serum, but not by a nonimmune serum. Both Concanavalin-A- and lipopolysaccharide-stimulated lymphocytes secrete an ACTH-like molecule with an antigenic specificity identical to pituitary-derived ACTH. Further, the amount of measurable immunoreactive ACTH was far lower than the amount of exogenously added ACTH required to evoke such a vigorous glucocorticoid response, suggesting that local deposition of the hormone results in a higher effective ACTH concentration. In addition, lymphocytes physically isolated from adrenal cells by a semipermeable membrane could stimulate steroidogenesis by 48 h, which corresponds to the rise in ACTH detected by RIA. These results confirm that activated lymphocytes synthesize as well as release biologically active ACTH, thus providing an in vitro model for a bidirectional communication between the endocrine and immune systems.

Adrenal Glands↗
PubMed1993

Pseudomonas aeruginosa keratitis in leukopenic rabbits.

To study the role of the host inflammatory response in Pseudomonas aeruginosa keratitis, rabbits were made leukopenic with intravenous injections of cyclophosphamide and dexamethasone. Twenty-four hr later, keratitis was initiated in all rabbits with an intrastromal injection of 1,000 log phase P. aeruginosa strain 27853. Slit lamp examination of eyes showed that leukopenic rabbits had significantly less (P < 0.0001) ocular pathology at 16, 22, and 27 hr postinfection. The number of viable bacteria recovered from corneas of leukopenic rabbits was the same as the number recovered from nonleukopenic rabbits (P = 0.95). These results suggest that the host inflammatory response significantly contributes to the overall ocular pathology associated with P. aeruginosa keratitis, but does not influence the survival of the infecting organism in the cornea at the height of the infection.

Animals↗
PubMed1993

Alpha adrenergic and mu-2 opioid receptors are involved in morphine-induced suppression of splenocyte natural killer activity.

The immunosuppressive effects following acute morphine administration have been mapped to opioid receptors in the central nervous system, specifically to the periaqueductal gray matter of the mesencephalon. The mesencephalon is associated with sympathetic neuronal processes, and the spleen is innervated with sympathetic neurons that are in direct apposition with lymphocytes in the periarteriolar lymphatic sheath. Accordingly, we investigated adrenergic involvement following morphine administration on natural killer (NK) activity by splenic lymphocytes. Acute morphine administration (25 mg/kg s.c.) suppresses (30-50%) NK activity by murine splenic immunocytes as measured in a 4-hr 51Cr-release assay. The suppression is blocked by phentolamine (4 mg/kg) and propranolol (10 mg/kg) in a dose-dependent fashion. However, phentolamine (2 mg/kg), but not propranolol (5 mg/kg), can also effectively antagonize morphine-induced immunosuppression. In addition, phentolamine (4 mg/kg) and prazocin (1 mg/kg), but not yohimbine (1 mg/kg), antagonizes morphine-elicited suppression of splenic NK activity. Selective opioid receptor antagonists were also utilized to determine the type or subtype of receptor activated following morphine administration. beta-Funaltrexamine (40 mg/kg) but not naloxonazine (35 mg/kg), naltrindole (20 mg/kg) or norbinaltorphimine (10 mg/kg) effectively blocks morphine-induced suppression of splenic NK activity. Collectively, morphine interacts with 1) mu-2 opioid receptors (most probably centrally) and 2) activates both alpha and beta adrenergic pathways.

Animals↗
PubMed1991

[An investigation of HSV-1 antigen in human corneas with recurrent HSK].

The authors first report in China the detection of HSV-1 antigen in 36 human corneas with recurrent HSK, using the horse radish peroxidase staining technique. The results were that in 16 eyes of quiescent HSK, the HSV antigen was negative, and in 11 of 20 corneas with active HSK, the HSV antigen was positive. When 5 corneas with quiescent HSK were cultured in vitro, 3 again became HSV antigen positive. The findings may be useful in the treatment of HSK.

Antigens, Viral↗
PubMed1990

Cyclosporine-containing collagen shields suppress corneal allograft rejection.

Thirty-seven rabbit eyes with penetrating keratoplasty grafts placed in vascularized beds to enhance the possibility of graft rejection were treated with cyclosporine delivered in collagen shields or drops of olive oil. Treatment was begun either immediately after grafting or at the first sign of immune graft reaction. Mean survival time of the grafts in the collagen shield treated eyes was significantly longer than in the eyes treated with drops. In the eyes treated at the first sign of graft reaction, cyclosporine in collagen shields halted the rejection process; seven of these eyes survived the 120-day observation period, compared to one of the eyes treated with drops. These results indicate that the collagen shield is an effective delivery system for cyclosporine and the topically administered cyclosporine is effective in suppressing the initiation of graft rejection and in reversing a graft reaction in progress.

Administration, Topical↗
PubMed1990

Cellular neuroimmunologic responses to ocular herpes simplex virus infection.

Infectious herpes simplex virus type 1 (HSV-1) was cultivated from the trigeminal ganglion between days 3 and 21 after ocular infection. T lymphocytes were first seen 9 days after infection and were present in ganglia collected 21 days after corneal infection. Neuron cell bodies expressing cytoplasmic HSV-1 antigens were present in the ganglion by 6 days after infection and could be found up to 21 days after infection although the frequency was low and decreased with time. Neuron cell bodies containing nuclear viral DNA were seen with the same frequency as cells expressing cytoplasmic viral antigens. T lymphocytes were seen surrounding neuron cell bodies some of which contained either cytoplasmic HSV-1 antigens or nuclear HSV-1 DNA.

Animals↗
PubMed1990

Effect of excimer laser energy on the growth potential of corneal keratocytes.

To determine whether exposure to the excimer laser beam results in the oncogenic transformation of cornea cells, tissue-cultured corneal keratocytes and intact corneas from an inbred strain of rat were exposed to ablative and subablative energies of the excimer laser beam. No evidence for cellular transformation was found. Neither the corneas nor the stromal keratocytes exposed to the laser beam were transformed into cells with unregulated growth potential. Both treated keratocytes and corneas were implanted subcutaneously in the same strain of rats; neither developed into tumors. In tissue culture, cells from cultures exposed to the excimer laser beam exhibited normal growth patterns, growing at the same rate as control, unexposed cells and exhibiting the same capacity to respond to the contact inhibition of growth as the control cells. These results suggest that the 193-nm excimer laser beam does not transform corneal keratocytes and that the energies emitted by this beam will not cause cell transformation when the excimer laser is used as a surgical tool in human eyes.

4-Nitroquinoline-1-oxide↗
PubMed1990

The role of class II antigen-expressing cells in corneal allograft immunity.

The goal of this study was to investigate the relationship between the presence of Class II antigen-expressing cells (Class II+) cells in the cornea and the generation of allograft immunity. Wistar/Furth (W/F) rat Class II+ cells were injected in various numbers (0.01, 0.1, 1.0, 5.0, 10.0, and 20.0 X 10(6) into the corneal stroma of Fischer 344 (F344) rats. For comparison, the same numbers of W/F Class II+ cells were injected directly into the peritoneal cavity of F344 rats. Also, W/F cells were injected into the corneas of F344 rats and the corneas were "grafted" intraperitoneally in F344 hosts. The results showed that up to 20 X 10(6) class II+ cells injected in situ into the corneal stroma did not elicit a serum cytotoxic antibody response or a splenic or blood cytotoxic T-cell response against donor Class II antigens. In contrast, systemic immune responses were elicited by both direct intraperitoneal injection of large numbers (10 or 20 X 10(6] of allogeneic Class II+ cells and by intraperitoneal grafting of syngeneic corneas carrying similar numbers of allogeneic Class II+ cells. F344 recipients of a syngeneic cornea containing 10 or 20 x 10(6) W/F Class II+ cells or a suspension of W/F cells exhibited an accelerated rejection of W/F skin allografts (13.3 versus 9.0 days, first- versus second-set rejection). These results indicate that the number of Class II+ cells required to elicit a systemic immune response is larger than the number of Class II+ cells present in the normal cornea.

Animals↗
PubMed1990

The collagen shield. A new vehicle for delivery of cyclosporin A to the eye.

Collagen shields were tested as a means of delivering the immunosuppressive drug, cyclosporine A (CsA), to the cornea and aqueous humor in rabbit eyes. Gelatinous collagen was mixed with crystalline CsA and then, during drying, was formed into contact lens-shaped shields which were applied to rabbit eyes. The amount of CsA in the corneas and aqueous humor (AH) samples from shield-treated eyes was compared with samples from rabbit eyes treated with CsA in olive oil. CsA concentrations were measured by radioimmunoassay (RIA) at 2, 4, and 8 h after application of the shields or drops. Both the corneal and aqueous humor concentrations of CsA achieved with the shield delivery system were 10-fold higher than those obtained with topical CsA-olive oil drops. The CsA levels achieved in the cornea using the collagen shield are sufficient to inhibit cellular immune reactions in vivo. These results demonstrate that collagen shields may be useful as an ocular delivery system for the drug CsA.

Analysis of Variance↗
PubMed1989

A simplified technique for the short-term tissue culture of rabbit corneal cells.

A technique for the short-term culture of pure populations of rabbit corneal endothelial and epithelial cells has been developed. Rabbit corneas were placed on concave agarose surfaces, treated briefly with a solution of trypsin and ethylenediamine tetracetic acid, and transferred, either epithelial cell surface or endothelial cell surface down, to microscope slide culture chambers. Within 6 to 12 h the epithelial cells or endothelial cells attached to the slide chamber surface and the cornea was removed, leaving behind a pure population of cells which spread out and grew to fill the surface of the slide chamber. This technique provides a simple and economic means for the reproducible initiation of primary cultures of rabbit corneal epithelial and endothelial cells for us in a variety of experiments.

Animals↗
PubMed1988

Cell-mediated immunity in the cornea.

An alternative model for corneal allografting termed the reverse corneal allograft reaction (RCAR) was developed in this study. Spleen cells from an alloimmunized donor were injected into the corneal stroma of the immunizing donor strain or were restimulated in mixed lymphocyte culture and then injected into the corneal stroma of the immunizing strain. The reaction began as a circular opaque site that spread and became irregularly shaped during the first 5 days after cell injection. The epithelial surface of the cornea became uneven and epithelial cell erosions were noted. Histological examination revealed that corneal stromal keratocytes at the site of inoculation had undergone degeneration and the injected cells had migrated toward the epithelial-stromal boundary, wherein a disruption of the basement membrane and disintegration of the epithelial cells occurred. Purified spleen cell subsets injected separately did not mediate the reaction. A suspension of T lymphocytes and class II antigen-positive macrophagelike cells was required to cause the RCAR. This reaction, which mimics a delayed-type hypersensitivity response, was transient, reaching a peak by day 5 and waning by day 8. This experimental model of the corneal allograft reaction shows promise for the study of cells and mediators of the corneal allograft reaction and can be employed as a reproducible system in which to test drug therapies for the treatment of corneal allograft rejection.

Animals↗
PubMed1988

The immunogenicity of corneal stromal keratocytes.

The purpose of this investigation was to compare the immunogenicity of corneal stromal keratocytes with that of splenic lymphocytes. The corneal stromal keratocytes of two inbred strains of rats were propagated in tissue culture in sufficient numbers to immunize allogeneic recipients and to determine the numbers of these cells required to elicit an allogenic immune response in the recipient. At least 30 x 10(6) tissue culture-propagated keratocytes injected intraperitoneally were required to elicit an alloantigenic response in the recipient strain. This alloantigenic response was measured by determining both the titer and specificity of serum alloantibody and by assessing the cellular immune response generated in the alloimmunized recipients. The results indicate that corneal stromal keratocytes can elicit both an antibody-mediated and a cell-mediated immune response, as indicated by the presence of serum antibody and cytotoxic lymphocytes in immunized recipients. The alloantibody and cellular immune responses were directed against the class I histocompatibility antigens of the immunizing strain. Class II antigens were not detected on the cultured keratocytes.

Animals↗