John E. Humphries

Arterial Thrombin Activity After Angioplasty in an Atherosclerotic Rabbit Model Time Course and Effect of Hirudin

BACKGROUND A 2-hour infusion of the direct thrombin inhibitor hirudin at the time of balloon angioplasty limits restenosis in the focally atherosclerotic rabbit. Although short-term administration of hirudin may have a prolonged biological effect, the effect of hirudin on vessel thrombin activity has not been previously studied in an animal model of angioplasty. We hypothesized that a short intravenous infusion of hirudin would result in prolonged inhibition of arterial wall-associated thrombin activity (ATA) after angioplasty. METHODS AND RESULTS Sixty-one rabbits received recombinant hirudin (r-hirudin)(1 mg/kg bolus plus 1 mg x kg(-1) x h(-1)x2hours) or bolus heparin (controls, 150 U/kg) intravenously at the time of femoral balloon angioplasty. ATA was measured through exposure of arterial segments ex vivo to fibrinogen and conducting an assay for fibrinopeptide A (FPA). ATA was low in nonballooned, atherosclerotic vessels (FPA=0.5+/-0.3 ng x mL(-1) x mg(-1)) but increased significantly at 24 hours after angioplasty in the heparin group (3.7+/-0.9 ng x mL(-1) x mg(-1), P<.01 versus baseline, n=9) but not in the hirudin group (FPA = 1.4+/-0.3; P=NS versus baseline, P<.02 versus heparin controls, n=8). The time course of ATA after angioplasty was assessed in 44 rabbits. Thrombin activity peaked at 48 hours and declined to baseline at 72 hours and 7 days. FPA values between the heparin and r-hirudin groups were similar at these later time points. CONCLUSIONS A 2-hour intravenous infusion of r-hirudin suppressed ATA measured 24 hours after angioplasty in the focally atherosclerotic rabbit. This prolonged biological effect may account, in part, for the reduction in restenosis seen in this model.

Anemia of renal failure: Use of Erythropoietin

Chronic renal failure is almost invariably accompanied by symptomatic anemia. It has been demonstrated that the primary cause of this anemia is inadequate production of erythropoietin by the diseased kidneys. The isolation of erythropoietin, followed by the cloning and expression of the human erythropoietin gene, made possible clinical trials of rHuEPO in uremic patients. rHuEPO produced dramatic increases in the hematocrit in almost all patients treated and also ameliorated many symptoms, such as lethargy, dizziness, and poor appetite, that had long been attributed to the effect of uremic toxins. Adverse effects of treatment with rHuEPO noted in the early clinical trials included hypertension, seizures, arteriovenous fistula or shunt thrombosis, and hyperkalemia. Further study of rHuEPO has shown that many of these side effects may be no more frequent in patients receiving rHuEPO than in other uremic patients not receiving rHuEPO. Reduction of the rHuEPO dosage and subcutaneous administration produce less rapid increases in the hematocrit and may lessen the incidence and severity of these side effects. rHuEPO therapy places great demands on both the bodys iron stores and the capacity to rapidly transfer iron from storage sites to the erythroid progenitor cells. Thus, almost all patients treated with rHuEPO become iron deficient and require oral or parenteral iron replacement. Response to rHuEPO in uremic patients is diminished if the anemia is complicated by iron deficiency, inflammatory disorders, aluminum overload, or deficiency of folate or vitamin B12. rHuEPO therapy is safe and effective in the treatment of the anemia of chronic renal failure. The use of rHuEPO leads to enhanced quality of life and eliminates the need for red cell transfusions. In addition to hemodialysis patients, predialysis patients and those on CAPD benefit from and are candidates for rHuEPO therapy.

Heparin Skin Necrosis: Delayed Occurrence in a Patient on Hemodialysis

A case of skin necrosis in a patient receiving intravenous (IV) heparin during routine intermittent hemodialysis is reported. Multiple erythematous, tender lesions developed over the abdomen and thighs and rapidly became necrotic. Biopsies showed fibrin thrombi in the dermal venules and capillaries, but no cellular infiltrate. The patient was in her third month of regular hemodialysis. Skin necrosis associated with the use of heparin usually occurs within 2 weeks of beginning heparin therapy and has not been reported in patients receiving heparin with hemodialysis. Possible mechanisms, including acquired antithrombin III deficiency leading to heparin-induced skin necrosis, are discussed.

Local adenovirus-mediated delivery of hirudin in a rabbit arterial injury model

Intravascular delivery of an E1/E3 deleted adenovirus encoding the hirudin protein reduces neointimal formation in the rat arterial injury model. Given the interspecies variability in response to adenoviral vectors, we tested this same construct in the hirudin-sensitive cholesterol-fed rabbit arterial balloon injury model. We hypothesized that local delivery of an E1/E3-deleted adenovirus encoding hirudin (Ad-Hir) in addition to early hirudin infusion would limit neointimal formation compared to early hirudin alone. Methods and Results: Local delivery of Ad-Hir, 2.5 × 1010 PFU/ml, using a double balloon catheter [n = 6 vessels (v)] produced a 79% reduction in vessel wall thrombin activity at 48 h after balloon angioplasty (BA) compared with vehicle (Veh, n = 6v; p = 0.05). In chronic experiments, hypercholesterolemic rabbits underwent femoral BA, and received either early hirudin alone (n = 9v) or early hirudin plus locally delivered Ad-Hir (early hirudin + Ad-Hir; n = 9v), an E1/E3-deleted adenovirus encoding β-galactosidase (early hirudin + AdGal; n = 7v), or Veh (early hirudin + Veh; n = 10v). Early hirudin + Ad-Hir did not limit the arterial response to injury versus the other groups at 4 weeks after BA. Plaque area, cross-sectional luminal area narrowing by plaque, and T cell infiltration were significantly increased in the adenovirus- versus non-adenovirus-treated arteries. Plaque area correlated with T cell density. Conclusion: Following BA in cholesterol-fed rabbits, local transduction with A-Hir produced a marked reduction in vessel wall-associated thrombin activity. However, this strategy increased rather than decreased the arterial response to BA injury. Our results suggest that the lack of therapeutic effect resulted from adenovirus-stimulated plaque formation, possibly resulting from a T cell-mediated inflammatory response.

Case Report: Sickle Cell Trait and Recurrent Deep Venous Thrombosis

Thromboembolic events are unusual in patients with sickle cell trait, particularly in the absence of hypoxic stresses. A young black man with multiple episodes of lower extremity deep venous thrombosis, the first of which occurred when he was 18 years old, is reported. The only identifiable risk factor for recurrent venous thrombosis was the presence of sickle cell trait.

Fibrinogenolytic and fibrinolytic activity of cell-associated plasmin.

Binding of plasmin(ogen) to rat C6 glioma cells is saturable and kringle-domain dependent. This interaction was studied as a model of plasmin(ogen) receptor interactions in nucleated mammalian cells. Apparent 125I-plasmin dissociation from C6 cell binding sites was slow; however, the dissociation rate was increased when the solution contained diisopropyl phosphoryl-plasmin (0.3 microM), fibrinogen (0.16 or 0.8 mg/ml), 1.08 mM D-Val-L-Leu-L-Lys-p-nitroanilide-HCl (S-2251), or epsilon-amino-n-caproic acid (EACA, 5.0 mM). EACA promoted the most rapid dissociation of plasmin. C6 cell-associated plasmin and plasmin in solution demonstrated similar amidase activity. Only specifically bound plasmin (75% of total binding) was active against S-2251. Plasmin that was initially bound to C6 cells digested fibrinogen in a time- and plasmin concentration-dependent manner. alpha 2-Antiplasmin (alpha 2AP, 0.1 microM) completely inhibited fibrinogenolysis by plasmin that was initially C6- or human umbilical vein endothelial-cell associated. Since alpha 2AP reacts selectively with plasmin in solution (minimally with plasmin bound to cells), fibrinogen digestion by cell-associated plasmin probably occurred only after the plasmin dissociated into solution. Crosslinked fibrin clots were formed in uniform layers over C6 cells. If the cells were incubated with plasmin before addition of fibrinogen and thrombin, the clots were rapidly lysed. alpha 2AP incompletely inhibited fibrinolysis when added after fibrin polymerization (44% inhibition with 0.1 microM alpha 2AP). Fibrinolysis was completely inhibited when alpha 2AP was added before fibrin polymerization. These studies suggest that plasmin must first dissociate from cellular binding sites to mediate fibrinogenolysis or fibrinolysis.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Bilateral Parotitis during Chemotherapy for Acute Lymphoblastic Leukemia

John E. Humphries, MD, Department of Pathology, Box 214, University of Virginia Health Sciences Center, Charlottesville, VA 22908 (USA) Shpilberg et al. [1] recently presented a 62-year-old man who developed recurrent bilateral parotitis during chemotherapy for acute myelogenous leukemia. The development of parotitis was attributed to the chemotherapy, which consisted of cytarabine and daunorubicin. We observed a similar phenomenon during the treatment of a young man with acute lymphoblastic leukemia. A 23-year-old male with acute lymphoblastic leukemia was admitted for chemotherapy and placement of an Ommaya reservoir. He received 10 days of L-asparaginase (500 IU/kg/day) with prednisone (100 mg p.o. per day for 7 days). On the 9th hospital day an Ommaya reservoir was placed without incident. Because of the presence of lymphoblasts on the peripheral blood smear, cytarabine (100 mg/m2 by continuous infusion for 7 days) and daunorubicin (45 mg/m2 i.v. for 3 days) were begun on the 11th hospital day. Methotrexate (12 mg) was administered through the reservoir on the 14th hospital day. On the 6th day of cytarabine (hospital day 18) the patient noted the acute onset of pain, tenderness and swelling in the parotid region bilaterally. Apart from bilateral parotid swelling, examination of the head, ears, nose and throat was unremarkable. The results of serum amy-lase determination are shown in figure 1. A serum lipase was normal (5 IU/dl; normal range 4-24 IU/dl), suggesting that the parotid glands rather than the pancreas were the source of the dramatic rise in serum amylase. Cytarabine infusion was completed the next day and within 2 days the swelling and discomfort had spontaneously resolved. Cyclocytidine, a chemotherapeutic agent which must first be converted in vivo to cytarabine to become active, induces parotid pain and sialorrhea [2]. These adverse effects appear to be primarily mediated through action on 1000 L-asparagmase 800 Cytarabine

Pulmonary Resection for Treatment of Cavitary Pulmonary Infarction

This article presents a case of cavitary pulmonary infarction, reviews the predisposing factors and possible complications, and gives recommendations on the treatment of this entity based on a review of the literature.

Immunoglobulin gene rearrangement in multiple myeloma: Limitations of southern blot analysis

Thirty-six patients with early and advanced multiple myeloma were investigated with Southern blot analysis to determine the presence of immunoglobulin gene rearrangement as evidence of clonality. Rearrangements were not uniformly found, being detected in only 14 of 19 patients with newly diagnosed myeloma and in 15 of 17 cases of clinically advanced myeloma. A correlation between percentage of bone marrow plasma cells and detection of immunoglobulin gene rearrangement was noted; however, in four cases of early myeloma with > 10% marrow plasma cells, no rearrangement was found. These results suggest that Southern blot analysis may not be an optimal method for the determination of clonality in plasma cell dyscrasias or, alternatively, that a proportion of the plasma cells found on bone marrow examination in some patients with early myeloma may not be monoclonal.

Trisomy 19 in a patient with myelodysplastic syndrome and thrombocytosis

A patient with refractory anemia with excess blasts, ringed sideroblasts, and thrombocytosis was found on cytogenetic analysis to have trisomy 19 as the sole abnormality. Although trisomy 19 in combination with other chromosomal anomalies has been encountered in association with a variety of hematologic malignancies, many solid tumors, and the myelodysplastic syndrome, its occurrence as the only cytogenetic aberration is rare and has not been reported in association with thrombocythemia.