Glucocorticoid-induced osteonecrosis is a common and dose-limiting adverse event. The goal of this study was to establish a mouse model of glucocorticoid-induced osteonecrosis suitable for testing the effects of different treatment strategies on its frequency. Fourteen murine strains were screened using various glucocorticoids, routes of administration, and diets. Four-week-old male BALB/cJ mice were treated with oral dexamethasone for up to 12 weeks either by continuous dosing or by discontinuous dosing, with or without asparaginase. Histopathological features of the distal femurs were examined by light microscopy. Osteonecrotic lesions were characterized by empty lacunae and osteocyte ghosts in trabecular bone surrounded by necrotic marrow and edema. The incidence of dexamethasone induced osteonecrosis in BALB/cJ mice was 40-45% (4/10 or 5/11) at 12 weeks. The frequency of osteonecrosis trended lower after discontinuous compared to continuous dosing for 12 weeks (8 vs. 45%) (p ¼ 0.06) despite comparable cumulative plasma exposure. Asparaginase hastened the occurrence of osteonecrosis, which was observed as early as 4 weeks and the incidence was 50% after 6 weeks. A mouse model of glucocorticoid-induced osteonecrosis was established. Discontinuous was less osteonecrotic than continuous dexamethasone treatment, consistent with the possible benefits of a ''steroid holiday'' seen in clinical settings. Moreover, asparaginase hastened osteonecrosis, indicating that drugs may interact with glucocorticoids to affect osteonecrosis risk. ß

Hepatopoietin-A (HPTA) is a heparinbinding polypeptide growth factor which consists of a heavy and a light polypeptide chain with molecular weights of 70,000 and 35,000, respectively. It stimulates DNA synthesis in primary cultures of normal rat hepatocytes in serum-free medium. The complete purification and characterization of HPTA from rabbit serum were reported by us elsewhere. Recently we have determined the amino-terminal amino acid sequence of the rabbit HPTA light chain up to 24 residues and have shown that the sequence is not homologous with other known sequences. [N.B. Human hepatocyte growth factor, recently sequenced by two other groups, is the same molecular species as HPTA.] In the present paper we report the production of a neutralizing polyclonal antiserum raised in chicken against purified rabbit HPTA. This antiserum does not inhibit the mitogenic effect of other potent inducers of hepatocyte DNA synthesis (epidermal growth factor or acidic fibroblast growth factor), nor does it interact with these growth factors in an enzyme-linked immunosorbent assay (ELISA). The antibody recognizes HPTA, as was determined by Western immunoblotting. Since the tissue origin of HPTA is not known, this anti-HPTA antiserum was used to investigate the tissue distribution of HPTA in rabbits by immunohistostaining methods. Acinar cells of the pancreas, neurons of the brain, C cells of the thyroid, ductal cells of the salivary glands, and Brunners glands of the duodenum stained with anti-HPTA antibody. Liver, spleen, thymus, and kidney do not seem to contain appreciable amounts of HPTA. We confirmed these fin gs by extracting and purifying active HPTA from the stained tissues listed above. The anti-HPTA antibody recognizes HPTA purifiled from different tissues, as was determined by ELISA, Western immunoblotting, and immunoneutralization experiments. We have also determined the sequence of the first 24 amino acids of the amino terminus of the light chain of rabbit HPITA and have shown that there is no homology between this sequence and the sequences of any known proteins and polypeptide growth factors (7). Growth factors with properties similar to those of HPTA have also been purified from human plasma or rat platelets by others (8,9).In the present paper we describe the production of a neutralizing polyclonal antibody raised in chicken against purified rabbit HPTA and the establishment of an enzymelinked immunosorbent assay (ELISA) for detection of nanogram quantities of this growth factor. This antiserum was used to investigate the tissue distribution of HPTA in rabbits. MATERIALS AND METHODSExtraction and Purification of HPTA from Different Rabbit Tissues. Rabbit pancreas, thyroid, pituitary, submaxillary gland, parotid gland, intestinal mucosa, spleen, and brain (from 25-50 rabbits) were purchased from Pel-Freez Biologicals. Frozen tissues were homogenized in extraction buffer consisting of phosphate-buffered saline (PBS; NaCI, 8.8 g/l; NaH2PO4 H2O, 0.2 g/l; Na2HPO4, 1.4 g/l), pH 7.4, containing 1 mM phenylm...

Little is known about how the mode of respiratory virus transmission determines the dynamics of primary infection and protection from reinfection. Using non-invasive imaging of murine parainfluenza virus 1 (Sendai virus) in living mice, we determined the frequency, timing, dynamics, and virulence of primary infection after contact and airborne transmission, as well as the tropism and magnitude of reinfection after subsequent challenge. Contact transmission of Sendai virus was 100% efficient, phenotypically uniform, initiated and grew to robust levels in the upper respiratory tract (URT), later spread to the lungs, grew to a lower level in the lungs than the URT, and protected from reinfection completely in the URT yet only partially in the lungs. Airborne transmission through 7.6-cm and 15.2-cm separations between donor and recipient mice was 86%–100% efficient. The dynamics of primary infection after airborne transmission varied between individual mice and included the following categories: (a) non-productive transmission, (b) tracheal dominant, (c) tracheal initiated yet respiratory disseminated, and (d) nasopharyngeal initiated yet respiratory disseminated. Any previous exposure to Sendai virus infection protected from mortality and severe morbidity after lethal challenge. Furthermore, a higher level of primary infection in a given respiratory tissue (nasopharynx, trachea, or lungs) was inversely correlated with the level of reinfection in that same tissue. Overall, the mode of transmission determined the dynamics and tropism of primary infection, which in turn governed the level of seroconversion and protection from reinfection. These data are the first description of the dynamics of respiratory virus infection and protection from reinfection throughout the respiratory tracts of living animals after airborne transmission. This work provides a basis for understanding parainfluenza virus transmission and protective immunity and for developing novel vaccines and non-pharmaceutical interventions.

A few reports indicated the incidence of hematolymphoid neoplasms in old CD-1 mice, but the cellular lineage of CD-1 mouse neoplasms has not be published. In this study, immunohistochemistry (IHC) was used to characterize the cellular lineage of spontaneous hematolymphoid neoplasms arising in young female CD-1 mice used as health monitoring sentinels and aging female CD-1 mice used as controls in 80 wk carcinogenesis studies. Lymphoblastic lymphomas of T-cell and B-cell lineage were common in mice 12 mo or less of age, whereas a wide range of non-lymphoblastic B-cell lymphomas and lymphoblastic T-cell lymphomas were common in mice > 12 mo old. Renal hyaline droplets positive for lysozyme were observed in aged mice with a histiocytic-associated large B-cell lymphoma (HA-BCL) and a myeloid leukemia. Endogenous ecotropic MuLV genes have been recovered from CD-1 mice, but MuLV protein expression has not been previously demonstrated. We reported for the first time the expression of MuLV protein by IHC in lymphomas and some normal tissues of both young and aging CD-1 mice. This report should help to differentiate spontaneous lymphomas and leukemias in CD-1 mice from those induced by chemicals and other methods.