Analysis of Vascular Endothelial Growth Factor (VEGF) and a receptor subtype (KDR/flk-1) in the liver of rats exposed to riddelliine: a potential role in the development of hemangiosarcoma

Riddelliine alters hepatocellular and endothelial cell kinetics and function including stimulating an increase in hepatocytic vascular endothelial growth factor (VEGF) in the absence of increased serological levels of VEGF (Nyska etal. 2002). The objective of this study was to further assess hepatic VEGF and KDR/flk-1 synthesis and expression by hepatic cells under riddelliine treatment conditions. Forty-two male F344/N rats were dosed by gavage with riddelliine (0, 1.0, and 2.5 mg/kg/day) for 6 weeks. Seven animals/group were sacrificed after 8 consecutive daily doses; remaining rats were terminated after 30 daily doses, excluding weekends. Hepatic tissues were evaluated by immunohistochemistry and in situ hybridization. The results showed that VEGF mRNA expression was observed in control and treated animals; however, qualitative differences were noted. Treated animals exhibited VEGF mRNA in clustered, focal hepatocytes and bile duct epithelium, whereas VEGF mRNA in hepatocytes from vehicle control rats was distributed evenly across all hepatocytes. Results evaluating the distribution of the VEGF cognate receptor, KDR/flk-1 showed that randomly distributed, rare sinusoidal endothelium, including those demonstrating karyomegaly and cytomegaly expressed KDR/flk-1. Phosphorylation of KDR/flk-1 at pTyr996 and pTyr1054/1059, but not pTyr951, was also detected, evidence that endothelial cell KDR/flk-1 was activated. These results suggest that both hepatocytes and endothelial cells are targets of riddelliine-induced injury. We speculate that damage to both populations of cells may lead to dysregulated VEGF synthesis by hepatocytes and activation of KDR/flk-1 by endothelium leading to the induction of sustained endothelial cell proliferation, culminating in the development of hepatic hemangiosarcoma.     

Characterization of the Sendai virus V protein with an anti-peptide antiserum.

The Sendai virus V protein, which is a fusion of the P and V ORFs of the P gene, was characterized with antisera to a portion of the V ORF and compared to the P protein. The only property found in common with P is that V is also highly phosphorylated, and this is so even when these proteins are expressed independently of the other viral proteins. Otherwise, V was not found in virions, was not strongly associated with viral nucleocapsids like P, and anti-V had no effect on viral RNA synthesis in vitro under conditions where anti-P was highly inhibitory. The available evidence suggests that V may play a role in RNA synthesis, but it is not an essential one like that of the P protein.     

Autoimmune vasculitis in MRL/Mp-lpr/lpr mice: orthochromatic basophils participate in the development of delayed-type hypersensitivity angiitis.

The pathogenesis of autoimmune vasculitis is poorly understood. Understanding the immunologic mechanisms governing this disease requires precise identification of the cells which comprise the lesion. In this report, we have evaluated tissue sections from MRL/lpr mice from 16 to 45 weeks of age, representing all stages of clinical vasculitis. We demonstrate that basophil myelocytes participate in the evolution of the delayed-type hypersensitivity (DTH) response which initiates and perpetuates autoimmune vasculitis in these mice. These findings raise questions regarding the immunologic mechanisms by which basophils develop in this lesion and the interaction of basophils. VSMCs and lymphocytes in vasculitic angiodestruction.     

"Worst case" aerosol testing parameters: I. Sodium chloride and dioctyl phthalate aerosol filter efficiency as a function of particle size and flow rate

The efficiency of filter media is dependent on the characteristics of the challenge aerosol and the filter's construction. Challenge aerosol parameters, such as particle size, density, shape, electrical charge, and flow rate, are influential in determining the filter's efficiency. In this regard, a so-called "worst case" set of conditions has been proposed for testing respirator filter efficiency in order to ensure wearer protection. Data collected on various types of filters (dust and mist; dust, fume, and mist; paint, lacquer, and enamel mist; and high efficiency) challenged with a worst case-type sodium chloride (NaCl) and dioctyl phthalate (DOP) aerosol are presented. The particle size of maximum penetration varies as a function of filter type and was less than 0.25-micron count mean diameter (CMD) in all cases. The count efficiency for high efficiency filters was greater than 99.97% at worst case testing conditions, but the worst case count efficiencies for dust and mist; dust, fume and mist; and paint, lacquer and enamel mist filters were not nearly as efficient as existing test methods indicate. Also, as the test flow rate is increased, the count efficiency decreases. Thus, respirator filters were found to conform to the prediction of single-fiber filtration theory.     

Comparison of serologic screening tests for brucellosis.

The slide agglutination test (SAT), microagglutination test (MAT), and card agglutination test (CAT) were compared with each other, using the tube agglutination test (TAT) as the standard method, by two reference laboratories to determine effectiveness as screening tests for human brucellosis. TAT titers of 1,253 sera tested in both laboratories were compared. In one laboratory, 1,270 sera were tested by the TAT and SAT, while the other laboratory tested 1,261 sera by both methods. Of these sera, 1,155 were tested in one laboratory by the CAT and 187 sera were tested by the MAT. Compared with that of the TAT (greater than or equal to 160 positive), the sensitivities were 97 to 100% (SAT), 90% (CAT), and 88% (MAT). The specificities were 88 to 89% (SAT), 98% (CAT), and 88% (MAT). For populations with a low prevalence of disease, increased specificity offers higher predictive value, so the CAT and MAT are preferable for screening purposes and the choice between tests depends on the number and frequency of tests performed. All sera reactive in the CAT and MAT should be retested with the TAT.     

Replication of the genome RNAs of defective interfering particles of vesicular stomatitis and Sendai viruses using heterologous viral proteins

We have tested the ability of heterologous viral proteins to support the in vivo and in vitro replication of the RNA of defective interfering (DI) particles of two serotypes of VSV and of Sendai virus. In all the combinations of heterologous coinfections in vivo, DI particle replication was observed only in the coinfection with the VSV-Indiana DI particle and wild-type VSV-New Jersey. By quantitating RNA synthesis in reconstitution experiments we showed that with DI nucleocapsids isolated from infected cells, however, the soluble protein fraction from heterologous wild-type virus-infected cells could substitute in vitro to varying degrees for the homologous proteins in the elongation reaction of RNA replication and encapsidation. In these cases successful replication was confirmed by demonstrating the specific association of the heterologous N protein with the product nucleocapsid RNA. The initiation step, that is, the initial binding of the nucleocapsid protein to the leader RNA, in contrast, requires the homologous protein, since heterologous viral proteins could not support RNA replication and encapsidation from purified DI particles.