Evaluating the effects of immediate application of negative pressure therapy after decompression from abdominal compartment syndrome in an experimental porcine model.

PURPOSE: The purpose of this large-animal study was to assess the safety and effects of negative pressure therapy (NPT) when used as temporary abdominal closure in the immediate post-decompression period after abdominal compartment syndrome (ACS). METHODS: Using a hemorrhagic shock/resuscitation and mesenteric venous pressure elevation model, ACS was physiologically induced in 12 female Yorkshire swine. At decompression, animals were allocated to either NPT (n = 6) or Bogota bag (n = 6) as temporary abdominal closure and studied for a period of 48 h or until death. Outcomes measured included morbidity and mortality, as well as hemodynamic parameters, ventilator-related measurements, blood gases, coagulation factors, and organ (liver, kidney, lung, and intestinal) edema and histology at the time of death/sacrifice. RESULTS: All animals developed ACS. Early application of NPT was associated with decreases in mesenteric venous and central venous pressure, and significantly increased drainage of peritoneal fluid. In addition, there was no increase in the incidence of mortality, recurrent intra-abdominal hypertension/ACS, or any deleterious effects on markers of organ injury. CONCLUSIONS: Early application of NPT in this porcine ACS model is safe and does not appear to be associated with an increased risk of recurrent intra-abdominal hypertension. The results of this animal study suggest that the application of NPT following decompression from ACS results in greater peritoneal fluid removal and may translate into augmented intestinal edema resolution secondary to more favorable fluid flux profiles.

Evaluation of the immunotoxicity of benzoporphyrin derivative (BPD-MA) in mice.

Photodynamic therapy has been shown to selectively eliminate activated lymphocytes in a number of experimental situations. These findings have important implications in therapies involving selective immunomodulation. In this study we report the effects of intravenous dosing with the photosensitizer benzoporphyrin derivative-monoacid A(BPD) on normal immunological function. Therapeutic doses of BPD and light had no effect on natural killer cell activity, the mixed lymphocyte reaction, cell-mediated lympholysis, the primary immune response to sheep red blood cells, or the secondary memory response to T cell-dependent antigens. In non-light treated controls, BPD at concentrations up to 10-fold higher had a limited effect on cell-mediated lympholysis. We conclude that the primary effect of BPD in several therapeutic modalities in not due to a generalized suppression of the immune system.

A review of the toxicology profile of rioprostil.

The toxicity of rioprostil was extensively investigated. Studies in rodents, dogs and monkeys indicate a low order of acute toxicity. Oral subchronic and chronic toxicity studies in rats and dogs produce effects that would be expected based on the pharmacological activity of the compound. In reproduction studies with rioprostil, male and female fertility is unaffected in rats at doses up to 2.0 mg/kg/day and there is no evidence of embryotoxicity, fetotoxicity, or teratogenicity in rats at doses up to 1.7 mg/kg/day. In rabbits a maternally toxic dose (1.5 mg/kg) also increases resorptions, reduces fetal weight, and increases the incidence of malformations. Evaluation of 24-month carcinogenicity studies in mice and rats at oral doses up to 2.0 and 1.5 mg/kg/day, respectively, are in progress. Mutagenicity studies are negative.

Use of the popliteal lymph node enlargement assay to measure rat T cell function in immunotoxicologic testing.

Modifications to the host vs graft response assay (HvGR) which render this technique suitable as an in vivo screen of cell-mediated immune function are described. This method utilizes mitotically inactivated spleen cells from normal heterozygous "nude" rats as stimulator population. We injected these cells into the left hind foot pad of unsensitized Charles River CD rats. Within one week, the recipients are sacrificed and both popliteal lymph nodes removed and weighed. The difference in weight between the challenged and unchallenged node represents the primary T cell response to the injected antigen sequestered in the draining lymph node. Using the immunosuppressive agents cyclophosphamide and dexamethasone we demonstrate the applicability of this assay to detect impaired cell-mediated immune function.

Induction of humoral immunity to protein antigen without adjuvant in rats exposed to immunosuppressive chemicals.

An experimental protocol was designed to assess humoral immune responses in animals antigenically challenged without the aid of adjuvants. The antigen selected was keyhole limpet hemocyanin (KLH). An enzyme-linked immunosorbent assay (ELISA) was utilized as the technique to measure serum antibody levels. The procedure was tested for sensitivity by use of a known immunosuppressant (cyclophosphamide), two metals (lead and selenium), and three chlorinated hydrocarbons (polychlorinated biphenyls, pentachlorophenol, and toxaphene). KLH without adjuvant provoked an adequate humoral immune response when assessed by the ELISA. The antibody response was greater on d 15 than on d 8 following primary KLH challenge, while secondary challenge resulted in an additional 10-fold increase in antibody levels. Cyclophosphamide suppressed the later primary response (d 15) and the secondary response more so than the early primary response (d 8). Of the 5 chemicals tested, 4 resulted in significantly impaired antibody levels to KLH at some time during the response. The magnitude of the immune response elicited to KLH is compared to that reported for bovine serum albumin and ovalbumin administered with Freund's adjuvant.

The differential sensitivity of rat peripheral blood T cells to immunosuppressants: cyclophosphamide and dexamethasone.

Peripheral blood T cells from rats given a single oral dose of dexamethasone (DMS) or cyclophosphamide (CY) exhibited a differential sensitivity to these compounds as measured by lymphoproliferation in the presence of concanavalin A (Con A) or phytohemagglutinin hemagglutinin (PHA). Con A-responsive cells (T Con A) were found to be resistant to the effects of DMS, while the PHA-responsive population (T PHA) showed a dose-dependent suppression at dose levels of 0.35 and 1.00 mg/kg. DMS did not alter serum antibody production against sheep erythrocytes at the dosage level which produced a significant depression of the PHA response. Animals treated with CY showed enhanced Con A-mediated lymphoproliferation at a dose of 15 mg/kg and marked suppression at 45 mg/kg. The PHA-mediated response, however, exhibited only a dose-dependent suppression at both dosage levels. CY had no effect on the antibody response at doses that enhance Con A lymphoproliferation. These results suggest that T helper cells and T suppressor cells are not TpHA cells.

Immunotoxicology in the pharmaceutical industry.

Development of an immunotoxicology program within the pharmaceutical industry is described. With few guidelines in the area and a multitude of factors to consider, a basic screen for evaluating immune competence in species routinely used in toxicologic studies has been proposed. The future of immunotoxicology depends upon the ability of the selected immune function tests to be predictive of human risk.

Cyclophosphamide induces osteopetrosis in rats.

The effect of a single oral dose of cyclophosphamide in six-week old random outbred albino rats on hematologic, immunologic, and pathologic parameters was studied. As expected, doses that decreased the number of circulating lymphocytes and suppressed the blastogenic response to Concanavalin A, a T cell mitogen, also caused extramedullary hematopoiesis in the liver and spleen and depletion of cortical lymphocytes in lymph nodes. However, a novel histomorphologic finding of this study was osteopetrosis. It would appear that cyclophosphamide interferes with a subpopulation of lymphoid cells that are involved in the formation of osteoclastic cells.

Ultraviolet carcinogenesis in T-cell-depleted mice.

The induction of skin tumors by chronic UV irradiation was compared in normal C3H/HeN(MTV-) mice, T-cell-depleted mice, and T-cell-depleted mice reconstituted with thymus grafts. The T-cell-depleted mice were thymectomized as young adults, lethally X-irradiated, and repopulated with neonatal liver cells. Skin tumors appeared earlier in the immunosuppressed T-cell-depleted mice than in the normal mice. However, tumors developed most rapidly in the group that was T-cell depleted and immunologically restored with thymus grafts. In the latter group, most of the tumors were squamous cell carcinomas, whereas in the normal mice, fibrosarcomas predominated. These experiments illustrated the limitations of this approach to studying the role of the immune response in carcinogenesis.

In vitro reactivity of macrophages and lymphocytes from ultraviolet-irradiated mice.

In these experiments we examined the ability of lymphocytes and macrophages from UV-treated mice of the inbred strain C3H/HeN(MTV-) to respond in vitro to nonspecific stimuli. Spleen and lymph node cells from UV-treated mice exhibited blastogenic responses to concanavalin A, phytohemagglutinin, and lipopolysaccharide that were equal to those of lymphoid cells from normal animals. Neither the induction of peritoneal exudate cells by inflammatory agents nor the phagocytic activity of peritoneal macrophages was affected by UV irradiation. Furthermore, no reduction occurred in the in vitro tumoricidal capacity of peritoneal macrophages from UV-treated mice after in vitro activation with xenogeneic lymphokines or endotoxin. We concluded that chronic UV irradiation does not lead to a generalized suppression of the immune system in mice.

Effects of trypan blue treatment on the immune responses of mice.

It has been reported that trypan blue treatment decreases the nonspecific resistance of mice to transplanted tumors and inhibits the in vitro cytotoxic activity of activated macrophages. We wished to determine whether this effect of trypan blue could be due to a selective inhibition of certain macrophage functions or whether it reflected a broader form of immunosuppression. We therefore tested the effects of trypan blue on a variety of immunological responses. Treatment of mice with trypan blue delayed their rejection of skin allografts and transplants of a highly antigenic syngeneic ultraviolet light-induced tumor. Trypan blue treatment of either donor or recipient decreased the local graft-versus-host reaction. Filtration of lymph node cells from trypan blue-treated donors on a nylon wool column before use in the graft-versus-host assay abrogated the depressive effect of trypan blue. A transient reduction in the blastogenic response of spleen cells to concanavalin A and lipopolysaccharide mitogens was observed after a single injection of trypan blue, but the response of lymph node cells was unaffected. The depressed response of splenic lymphocytes was not entirely reversed by removal of adherent cells. The primary and secondary hemagglutinin responses to sheep erythrocytes were unaffected in trypan blue-treated mice, and the proportion and phagocytic activity of thioglycolate-induced peritoneal macrophages were also unaltered. We conclude that treatment of mice with trypan blue selectively inhibits certain macrophage functions but, at high doses, it can also inhibit some lymphocyte activities.

In vitro stimulation and inhibition of tumor cell growth mediated by different lymphoid cell populations.

Spleen, lymph node and thymus cells from normal C57BL/6 mice or mice given injections 6 to 20 days previously with syngeneic methylocholanthrene-induced fibrosarcoma (B6MCA) cells were tested for their ability to mediate growth stimulation and/or inhibition of B6MCA cells in vitro. At an effector cell to tumor cell ratio of 10:1,, nucleated spleen cells from mice bearing the tumor for 6 days enhanced tumor cell growth. Neither lymph node nor thymus cells from tumor-bearing mice were stimulatory. Tumor cell growth was inhibited by either spleen or lymph node cells only when a ratio of 1000:1 was exceeded. Thymocytes, however, were inhibitory at a ratio of 100:1,. Lymphoid cells from normal mice were not stimulatory at low ratios or inhibitory at any ratio tested. Both stimulatory and inhibitory activities disappeared by Day 20. Filtration of sensitized spleen cells through a glass wool column did not remove stimulatory or inhibitory activities. Subsequent passage through a nylon wool column resulted in a loss of stimulation, but not inhibition, of tumor cell growth. Stimulatory activity was completely abrogated by treatment with either anti-theta or rabbit anti-mouse gamma-globulin serum. A 1:1 mixture of spleen cells treated with either antisera did not restore stimulation. Spleen cells from T-cell- or B-cell-deficient mice bearing the tumor for 6 days were also not stimulatory. The results suggest that immunostimulation of tumor growth in vitro is mediated by a lymphoid cell that is distinct from the cytotoxic effector cell.