The hematopathology of cefonicid- and cefazedone-induced blood dyscrasias in the dog

Total parenteral nutrition alters molecular and cellular indices of intestinal inflammation in neonatal piglets

BACKGROUND

The adverse effects of TPN on systemic immunity are well-documented; however, the impact of IV feeding on neonatal intestinal immunity is unknown.

METHODS

A piglet TPN model was used to compare immune cell composition within the intestinal epithelium and lamina propria of parenterally and orally fed piglets.

RESULTS

Small intestinal weight of piglets maintained intravenously was reduced 50% after 7 days. Intestinal atrophy in piglets fed parenterally was evidenced by decreased width of intestinal villi and colon cuffs and reduced intestinal crypt depth. The numbers of CD4+ and CD8+ T lymphocytes were threefold greater within the lamina propria of jejunal and ileal villi of piglets supported intravenously. Inverse correlations were observed between villus height or width and T-lymphocyte numbers (r = -.80; p < .05). Major histocompatibility complex class II mRNA expression, an indicator of localized inflammation, was increased in the ileum and colon of piglets receiving parenteral nutrition. Goblet cell numbers were two-fold greater in jejunal and ileal villi, and mast cells were more abundant in the colon of piglets fed parenterally. Furthermore, jejunal T-lymphocyte numbers were correlated with goblet cell numbers (r = .80; p = .01).

CONCLUSIONS

These data identify molecular and cellular indices of intestinal inflammation that are responsive to IV feeding in neonates and provide a novel framework to investigate mechanisms underlying gut atrophy during TPN.

A review of myelofibrosis in dogs

Myelofibrosis is a proliferative response of the bone marrow fibroblasts. Myelofibrosis can be classified as primary or secondary depending on the underlying etiology. Primary myelofibrosis is a myeloproliferative disorder in humans in which there is a clonal proliferation of a pluripotent stem cell. Hemopathology includes finding nucleated red blood cells and immature granulocytes in the circulation, extramedullary hematopoiesis, and myelofibrosis. The proliferation of the bone marrow fibroblasts is not clonal in origin. To the best of this author's knowledge, this type of myelofibrosis has not been reported to occur naturally in the dog. Secondary myelofibrosis has been reported in the dog associated with neoplastic conditions, irradiation, congenital hemolytic anemias, and a variety of unknown etiologies. It has been shown in some cases of myelofibrosis that there is often concurrent bone marrow necrosis. Bone marrow necrosis has been documented in dogs with Ehrlichiosis and septicemia, and associated with drug treatment, including estrogens and cephalosporins. It is though that this necrosis is due to the destruction of the bone marrow microvasculature and/or hematopoietic elements. Release of growth factors by inflammatory cells may lead to the subsequent fibroblast proliferation. Several cases of secondary myelofibrosis in female laboratory beagles have been recently observed. These dogs present with a severe nonregenerative anemia and often a mild neutropenia with varying degrees of myelofibrosis in the bone marrow. Some animals have had concurrent bone marrow necrosis. At this time, the exact etiology is unknown.

Experimental pancytopenia of the peripheral blood with granulocytopoietic bone marrow hyperplasia in the beagle-dog

During subacute and chronic toxicity studies on beagle dogs with the platelet aggregation inhibitor UH-A 46 XX, a suboxicam derivative, a pancytopenia of the peripheral blood with granulocytopoietic bone marrow hyperplasia was induced. Our observations are based on the results of a 13 week routine experiment (control group and dosage groups 5-, 50- and 700 mg/kg per day UH-A 46 XX) and on a special open-ended reversibility study (control group and dosage groups 50- and 700 mg/kg). The reversibility study included closely monitored hematological controls, bone-marrow cytology from sternal punctures and plastic section histology of iliac crest biopsies. During this study, plasma levels of the substance were estimated. The reproducible syndrome described was similar in the dogs in both studies. As early as the 8th week, but mostly between the 9th and 12th experimental weeks, one third of the animals treated orally with 700 mg/kg b.wt. UH-A 46 XX per day developed an acute fever (10 out of 30 animals). Four died several days later. Dogs treated with 5 or 50 mg/kg UH-A 46 XX remained unaffected. In the diseased dogs in both studies, proven pancytopenia was associated with the occurrence of numerous hematopoietic, especially granulocytopoietic precursors. The hyperplastic bone marrow showed a massive increase in granulocytopoiesis with considerable maturation arrest. These processes were accompanied by suppression or reduction of erythropoiesis. In addition, histological findings in the animals that died showed extramedullary hematopoiesis in different organs. During the second study, the reversibility was investigated in sick animals. If substance administration was terminated when the illness had reached its peak, normalization occurred quickly within 2 to 3 weeks. The animals remained healthy until the end of the long term follow-up which varied from 9 to 10 months. The pathogenesis of pancytopenia caused by UH-A 46 XX seems to be a chemically induced hyperdestruction of the peripheral blood cells. This appraisal is supported by the clear degenerative alterations in the granulocytic cells of the peripheral blood. An additional inhibitory effect of UH-A 46 XX on cellular maturation processes of hematopoiesis can be assumed.

Cephalosporin-induced immune cytopenia in the dog: demonstration of erythrocyte-, neutrophil-, and platelet-associated IgG following treatment with cefazedone

Cephalosporin treatment in man has been associated with a low incidence of hemolytic anemia, thrombocytopenia, and neutropenia; some cases have been shown to be immune-mediated. This triad of blood dyscrasias was also demonstrated in our laboratory in a series of toxicity studies in dogs of two cephalosporin compounds, cefonicid and cefazedone; these studies provided evidence for drug-associated immune hemolytic anemia, based on conventional laboratory tests. To further investigate possible immune mechanisms of the cephalosporin-induced cytopenias, we measured erythrocyte-associated, platelet-associated (PAIgG), and serum antineutrophil IgG over the course of cephalosporin treatment, using highly sensitive 125I-staphylococcal protein A (SPA) assays, as well as the direct antiglobulin test; we compared these findings with the hematologic changes. Intravenous treatment with high doses of cefazedone (540 mg/kg/day, increased to a maximum of 840 mg/kg/day for 4 months or until hematologic effects were evident) resulted in a high incidence of anemia (7/14), thrombocytopenia (11/14), and neutropenia (7/14). Of the affected dogs examined, 6/7 with anemia, 9/9 with thrombocytopenia, and 7/7 with neutropenia showed increased levels of the respective cell-associated antibody, compared with untreated controls. Unaffected dosed animals generally did not show these changes. In 3/3 dogs examined following remission of thrombocytopenia, PAIgG returned to levels comparable with controls; as one of these dogs suffered a relapse, increased PAIgG was again observed. Animals sacrificed during cytopenic episodes showed cytologic and histologic evidence of increased hemophagocytosis. We conclude that antibody-mediated blood cell destruction contributes to all three cephalosporin-induced cytopenias in the dog.

Cephalosporin-induced changes in the ultrastructure of canine bone marrow

Fourteen healthy dogs were given 540 to 840 mg/kg of cefazedone (Refosporen) intravenously for up to 4 months or until peripheral blood cell count were depressed. Within 6 to 10 weeks treated dogs developed pancytopenia (5/14), thrombocytopenia (11/14), moderate to severe neutropenia (8/14), and/or normocytic anemia with erythroblastemia (8/14). Ultrastructural changes in bone marrow of severely cytopenic dogs included mitochondrial damage in hematopoietic and nonhematopoietic cells, thickening of endosteal bone lining layers, increased adventitial coverage of vascular sinuses, and an increased number of active macrophages. Swollen, ruptured mitochondria were in erythroid, granulocytic, and megakaryocytic cells, and, to a lesser extent, in macrophages, reticular endothelial, and bone lining cells. Maturation arrest was evident in both erythroid and granulocytic cell lines. There was also evidence of ineffective erythropoiesis and granulopoiesis. None of these changes were observed in bone marrow of controls, treated dogs that did not develop cytopenia, or dogs allowed to recover after cessation of dosing.