Jennie W. Owens

Targeted disruption of the alpha isoform of the peroxisome proliferator-activated receptor gene in mice results in abolishment of the pleiotropic effects of peroxisome proliferators.

To gain insight into the function of peroxisome proliferator-activated receptor (PPAR) isoforms in rodents, we disrupted the ligand-binding domain of the alpha isoform of mouse PPAR (mPPAR alpha) by homologous recombination. Mice homozygous for the mutation lack expression of mPPAR alpha protein and yet are viable and fertile and exhibit no detectable gross phenotypic defects. Remarkably, these animals do not display the peroxisome proliferator pleiotropic response when challenged with the classical peroxisome proliferators, clofibrate and Wy-14,643. Following exposure to these chemicals, hepatomegaly, peroxisome proliferation, and transcriptional-activation of target genes were not observed. These results clearly demonstrate that mPPAR alpha is the major isoform required for mediating the pleiotropic response resulting from the actions of peroxisome proliferators. mPPAR alpha-deficient animals should prove useful to further investigate the role of this receptor in hepatocarcinogenesis, fatty acid metabolism, and cell cycle regulation.

The fusion gene Cbfb-MYH11 blocks myeloid differentiation and predisposes mice to acute myelomonocytic leukaemia.

The fusion gene Cbfb - MYH11 blocks myeloid differentiation and predisposes mice to acute myelomonocytic leukaemia

Carbonic anhydrase III is not required in the mouse for normal growth, development, and life span.

ABSTRACT Carbonic anhydrase III is a cytosolic protein which is particularly abundant in skeletal muscle, adipocytes, and liver. The specific activity of this isozyme is quite low, suggesting that its physiological function is not that of hydrating carbon dioxide. To understand the cellular roles of carbonic anhydrase III, we inactivated the Car3 gene. Mice lacking carbonic anhydrase III were viable and fertile and had normal life spans. Carbonic anhydrase III has also been implicated in the response to oxidative stress. We found that mice lacking the protein had the same response to a hyperoxic challenge as did their wild-type siblings. No anatomic alterations were noted in the mice lacking carbonic anhydrase III. They had normal amounts and distribution of fat, despite the fact that carbonic anhydrase III constitutes about 30% of the soluble protein in adipocytes. We conclude that carbonic anhydrase III is dispensable for mice living under standard laboratory husbandry conditions.

Isolation and experimental transmission of a reovirus pathogenic in ratsnakes (Elaphe species).

A reovirus was isolated from juvenile Moellendorffs ratsnakes (Elaphe moellendorffi) and beauty snakes (Elaphe taenuris) that died soon after importation into the USA. Viper heart (VH2) cells inoculated with tissue homogenates showed cytopathic effects consisting of large syncytia formation followed by cell detachment from the monolayer. Tissue culture supernatants failed to hemagglutinate guinea pig and chicken erythrocytes at room temperature. Electron microscopy of purified virions revealed spherical to icosahedral particles measuring 70-85 nm in diameter with a double capsid layer. Preparations of the viral genome contained ten segments of dsRNA when analyzed by polyacrylamide gel electrophoresis. A juvenile black ratsnake (Elaphe obsoleta obsoleta) was experimentally inoculated with the isolate and was found dead 26 days post inoculation. Necropsy revealed diffuse subacute interstitial pneumonia with respiratory epithelial cell hyperplasia and syncytia. Reovirus isolated from this snake was used to inoculate another juvenile black ratsnake which was euthanized 40 days post inoculation. Pneumonia and multifocal subacute proliferative tracheitis were found on necropsy. Reovirus was isolated from the lung of this snake and was demonstrated by transmission electron microscopy. This is the first documentation of a pathogenic reptile reovirus and the first report of experimental transmission of a reovirus in snakes.

Sertoli Cell Vacuolization and Abnormal Germ Cell Adhesion in Mice Deficient in an Inositol Polyphosphate 5-Phosphatase1

Abstract The dynamic nature of cellular interactions during differentiation of germ cells and their translocation from the basement membrane to the lumen of the seminiferous tubules requires the existence of complex and well-regulated cellular adhesion mechanisms in the testis. Successful migration of the developing germ cells is characterized by dynamic breakage and reformation of cadherin-containing adherens junctions between the germ cells and Sertoli cells, the polarized somatic cells of the testis that support and nourish the developing gametes. Here, we demonstrate the accumulation of abnormally swollen, actin-coated, endosome-like structures that contain intact adherens junctions and stain positive for N-cadherin and β-catenin in the Sertoli cell cytosol of mice deficient in Inpp5b, an inositol polyphosphate 5-phosphatase. Simultaneous to the formation of these abnormal structures, developing germ cells are prematurely released from the seminiferous epithelium and sloughed into the epididymis. Our results demonstrate a role for Inpp5b in the regulation of cell adhesion in the testis and in the formation of junctional complexes with neighboring cells, and they emphasize the important and essential role of phosphoinositides in spermatogenesis.

Paramyxovirus infection in caiman lizards (Draecena guianensis)

Three separate epidemics occurred in caiman lizards (Dracaena guianensis) that were imported into the USA from Peru in late 1998 and early 1999. Histologic evaluation of tissues from necropsied lizards demonstrated a proliferative pneumonia. Electron microscopic examination of lung tissue revealed a virus that was consistent with members of the family Paramyxoviridae. Using a rabbit polyclonal antibody against an isolate of ophidian (snake) paramyxovirus, an immunoperoxidase staining technique demonstrated immunoreactivity within pulmonary epithelial cells of 1 lizard. Homogenates of lung, brain, liver, or kidney from affected lizards were placed in flasks containing monolayers of either terrapene heart cells or viper heart cells. Five to 10 days later, syncytial cells formed. When Vero cells were inoculated with supernatant of infected terrapene heart cells, similar syncytial cells developed. Electron microscopic evaluation of infected terrapene heart cells revealed intracyto-plasmic inclusions consisting of nucleocapsid strands. Using negative-staining electron microscopy, abundant filamentous nucleocapsid material with a herringbone structure typical of the Paramyxoviridae was observed in culture medium of infected viper heart cells. Seven months following the initial epizootic, blood samples were collected from surviving group 1 lizards, and a hemagglutination inhibition assay was performed to determine presence of specific antibody against the caiman lizard isolate. Of the 17 lizards sampled, 7 had titers of <1:20 and 10 had titers of >1:20 and <1:80. This report is only the second of a paramyxovirus identified in a lizard and is the first to snow the relationship between histologic and ultrastructural findings and virus isolation.

Anti-Mouse Mesangial Cell Serum Induces Acute Glomerulonephropathy in Mice

In order to develop a model in mouse similar to anti- Thy-1 nephritis in the rat, we prepared sheep antiserum against SV40-transformed mouse mesangial (MES 13) cells. In vivo, the anti-mouse mesangial cell serum-treated mice showed severe azotemia that peaked at day 6 and proteinuria that peaked at day 8, in a dose-dependent fashion. Light microscopy and electron microscopy showed duplication of glomerular basement membranes, mesangiolysis, subendothelial and mesangial electron-dense deposits, and foot process effacement. Intraglomerular tuft cell number was significantly reduced at day 4 and there were increased numbers of apoptotic cells at days 2 and 4. SCID mice and mice lacking C3 manifested similar responses to anti-mouse mesangial cell serum, suggesting that T cells, B cells and complement are not required for glomerular injury in this model. In vitro, anti-mouse mesangial cell serum treated mesangial cells showed greater release of lactate dehydrogenase, decreased cell survival, and increased apoptotic cell death. Anti-mouse mesangial cell serum induces glomerulopathy characterized by mesangiolysis and mesangial cell apoptosis, and followed by cellular proliferation.