Anomalous portosystemic anastomoses associated with chronic hepatic insufficiency in six young dogs.

Chronic hepatic insufficiency due to anomalies of the portal venous system was diagnosed in 6 young dogs. The disorder was characterized by a variety of abnormal central nervous system signs or ascites, or both. Laboratory findings were characteristic of chronic, generalized hepatic dysfunction. The diagnosis was established by angiographic studies of the portal venous system. Of the 6 dogs, 3 died, 1 was euthanatized, and 2 are still alive and require medical management for ascites.     

Ophthalmomyiasis interna anterior in a dog: keratotomy and extraction of a Cuterebra sp. larva

A 1‐year‐old female spayed mixed‐breed dog was presented for evaluation of acute onset of lethargy and blepharospasm OD. Slit‐lamp biomicroscopy revealed a segmented larva embedded in the inferonasal iris. Moderate anterior uveitis was present. After pharmacologic dilation, mild vitreal hemorrhage and chorioretinal migration tracks were identified. The dog was treated empirically for uveitis for 5 days, after which a keratotomy and larval foreign body extraction was performed. The dog recovered uneventfully from intraocular surgery and remained visual and comfortable. Parasite evaluation confirmed the larva to be a Cuterebra sp. To the authors’ knowledge, this is the first report of canine ophthalmomyiasis interna anterior, and the first report of successful surgical removal from the anterior segment in a dog with preservation of vision.     

Identification of p53 as a sequence-specific DNA-binding protein

The tumor-suppressor gene p53 is altered by missense mutation in numerous human malignancies. However, the biochemical properties of p53 and the effect of mutation on these properties are unclear. A human DNA sequence was identified that binds specifically to wild-type human p53 protein in vitro. As few as 33 base pairs were sufficient to confer specific binding. Certain guanines within this 33-base pair region were critical, as methylation of these guanines or their substitution with thymine-abrogated binding. Human p53 proteins containing either of two missense mutations commonly found in human tumors were unable to bind significantly to this sequence. These data suggest that a function of p53 may be mediated by its ability to bind to specific DNA sequences in the human genome, and that this activity is altered by mutations that occur in human tumors.     

Human genome ultraconserved elements are ultraselected

Ultraconserved elements in the human genome are defined as stretches of at least 200 base pairs of DNA that match identically with corresponding regions in the mouse and rat genomes. Most ultraconserved elements are noncoding and have been evolutionarily conserved since mammal and bird ancestors diverged over 300 million years ago. The reason for this extreme conservation remains a mystery. It has been speculated that they are mutational cold spots or regions where every site is under weak but still detectable negative selection. However, analysis of the derived allele frequency spectrum shows that these regions are in fact under negative selection that is much stronger than that in protein coding genes.     

Stress and fold localization in thin elastic membranes

Thin elastic membranes supported on a much softer elastic solid or a fluid deviate from their flat geometries upon compression. We demonstrate that periodic wrinkling is only one possible solution for such strained membranes. Folds, which involve highly localized curvature, appear whenever the membrane is compressed beyond a third of its initial wrinkle wavelength. Eventually the surface transforms into a symmetry-broken state with flat regions of membrane coexisting with locally folded points, reminiscent of a crumpled, unsupported membrane. We provide general scaling laws for the wrinkled and folded states and proved the transition with numerical and experimental supported membranes. Our work provides insight into the interfacial stability of such diverse systems as biological membranes such as lung surfactant and nanoparticle thin films.     

Enzyme dynamics during catalysis

Internal protein dynamics are intimately connected to enzymatic catalysis. However, enzyme motions linked to substrate turnover remain largely unknown. We have studied dynamics of an enzyme during catalysis at atomic resolution using nuclear magnetic resonance relaxation methods. During catalytic action of the enzyme cyclophilin A, we detect conformational fluctuations of the active site that occur on a time scale of hundreds of microseconds. The rates of conformational dynamics of the enzyme strongly correlate with the microscopic rates of substrate turnover. The present results, together with available structural data, allow a prediction of the reaction trajectory.     

Sediment Budget Analysis for River Reservoirs

The sediment, budget of a reservoir on the Neckar River, Germany, was investigated by means of experimental and numerical methods. Field measurements of channel bathymetry show that. sedimentation and erosion occur primarily in the lower backwater-influenced section of the reservoir, which stores approximately 350,000 m³ of fine-grained deposits. Sediment load balances for two major storm events in Dec. 1993 and Apr. 1994 showed net erosion of 32,000 ±10,000 tonnes and 24,000 ± 5,000 tonnes of sediment, respectively. A balanced sediment budget, was found for a minor flood in Jan. 1995. In agreement with the field data, numerical simulation of sediment transport. over a period of 45 years demonstrates that the river reservoir served initially as a sediment trap from 1950 to 1978, and since then as a temporary storage basin for sediment.