Effect of different fixative solutions on eyes with experimental proliferative vitreoretinopathy

The aim of this study was to evaluate the use of different fixatives on the reliability of histopathological changes in a rabbit model of proliferative vitreoretinopathy (PVR). Twenty eyes from 10 rabbits were divided into four groups. The right eyes were used in two experimental groups (each n = 5), and the left, in two control groups (each n = 5). Using a newly developed scleral incision marker, an oblique scleral incision was standardized in the experimental groups, followed by intravitreal injection of 0.4 ml autologous blood and the left for wound repair for four weeks. Eyes were enucleated at four weeks. The groups differed in the type of used fixative solution (formaldehyde 4% vs. 1% buffered formaldehyde and 1.25% glutaraldehyde). The eyes were evaluated for the development of fibrosis, retinal detachment (RD), and processed for histopathology. Fibrous ingrowth of a variable degree was present in the experimental groups originating from the trauma site. Experimental eyes fixed with formaldehyde 4% had RD extension that was greater than that fixed in formaldehyde/glutaraldehyde mixture; however, the difference did not reach statistical significance (P = 0.15). This difference was not fully explained by the fibrosis which developed. In addition, in control groups, formaldehyde 4% induced a fixative-dependent retinal separation that was absent in eyes fixed with formaldehyde/glutaraldehyde mixture (P = 0.03). In conclusion, a mixture of buffered formaldehyde 1% and glutaraldehyde 1.25% combined with standardized scleral incision resulted in consistent pathological changes. A reliable PVR model is a condition sine qua non to evaluate antifibrotic treatment strategies.     

MLST of housekeeping genes captures geographic population structure and suggests a European origin of Borrelia burgdorferi

Lyme borreliosis, caused by the tick-borne bacterium Borrelia burgdorferi, has become the most common vector-borne disease in North America over the last three decades. To understand the dynamics of the epizootic spread and to predict the evolutionary trajectories of B. burgdorferi, accurate information on the population structure and the evolutionary relationships of the pathogen is crucial. We, therefore, developed a multilocus sequence typing (MLST) scheme for B. burgdorferi based on eight chromosomal housekeeping genes. We validated the MLST scheme on B. burgdorferi specimens from North America and Europe, comprising both cultured isolates and infected ticks. These data were compared with sequences for the commonly used genetic markers rrs-rrlA intergenic spacer (IGS) and the gene encoding the outer surface protein C (ospC). The study demonstrates that the concatenated sequences of the housekeeping genes of B. burgdorferi provide highly resolved phylogenetic signals and that the housekeeping genes evolve differently compared with the IGS locus and ospC. Using sequence data, the study reveals that North American and European populations of B. burgdorferi correspond to genetically distinct populations. Importantly, the MLST data suggest that B. burgdorferi originated in Europe rather than in North America as proposed previously.     

Translation initiation controls the relative rates of expression of the bacteriophage lambda late genes.

The late operon of bacteriophage lambda contains the genes encoding the morphogenetic proteins of the phage. These genes are transcribed equally from the single late promoter. Although the functional half-lives of the mRNA for the various genes of this operon vary less than 2-fold, their relative rates of expression have been shown to vary by nearly 1000-fold. This variation could result from differing rates of translation initiation, from overlapping upstream translation, or from differential elongation rates due to the presence of codons for which the corresponding tRNAs are rare. To distinguish between these possibilities, we have cloned sequences surrounding the initiator codons of several of these genes and measured their ability to drive synthesis of hybrid lambda-beta-galactosidase proteins. The rates of expression of the hybrid genes thus produced correlate very well with the natural rates of expression of the corresponding phage genes, suggesting that the rate of initiation of translation controls the relative expression rates of these genes.     

Protein cleavage in bacteriophage lambda tail assembly

The protein product of gene H, a tail gene of bacteriophage λ, undergoes proteolytic cleavage to yield protein t2, a structural component of λ tails.     

Inhibition of lysosomal degradation in retinal pigment epithelium cells induces exocytosis of phagocytic residual material at the basolateral plasma membrane

PURPOSE: To analyze chloroquine-induced morphological changes in the retinal pigment epithelium (RPE) and Bruch's membrane (BM). METHODS: Retina-choroid complexes of chloroquine-treated Long-Evans rats were analyzed by electron microscopy. RESULTS: Intercellular spaces between the RPE cells and BM were enlarged. Residual material from phagosomes was released into these enlarged spaces. Debris accumulated within BM and encircled choriocapillaris endothelial cells. CONCLUSION: There is a release of undegraded phagocytic material (rod outer segments) into the extracellular space between BM and RPE cells, following inhibition of lysosomal degradation. Electron-dense deposits in BM and choriocapillaris may lead to reduced oxygen and nutrition flow.     

Single-agent therapy with sorafenib or 5-FU is equally effective in human colorectal cancer xenograft—no benefit of combination therapy

Background

We initiated this preclinical study in order to analyze the impact of sorafenib single treatment versus combination treatment in human colorectal cancer.

Methods

The effect of increasing sorafenib doses on proliferation, apoptosis, migration, and activation of signal cascades was analyzed in vitro. The effect of sorafenib single treatment versus 5-fluorouracil (5-FU) single treatment and combination therapy on in vivo proliferation and target cytokine receptor/ligand expression was analyzed in a human colon cancer xenograft mouse model using HT29 tumor cells.

Results

In vitro, SW480 and HT29 cell lines were sensitive to sorafenib, as compared to Caco2 and SW620 cell lines, independent of the mutation status of K-ras, Raf, PTEN, or PI3K. The effect on migration was marginal, but distinct differences in caspases activation were seen. Combination strategies were beneficial in some settings (sorafenib?+?5-FU; irinotecan) and disadvantageous in others (sorafenib?+?oxaliplatin), depending on the chemotherapeutic drug and cell line chosen. Sensitive cell lines revealed a downregulation of AKT and had a weak expression level of GADD45β. In resistant cell lines, pp53 and GADD45β levels decreased upon sorafenib exposure. In vivo, the combination treatment of sorafenib and 5-FU was equally effective as the respective monotherapy concerning tumor proliferation. Interestingly, treatment with either sorafenib or 5-FU resulted in a significant decrease of VEGFR1 and PDGFRβ expression intensity.

Conclusions

In colorectal cancer, a sensitivity towards sorafenib exists, which seems similarly effective as a 5-FU monotherapy. A combination therapy, in contrast, does not show any additional effect.     

Cowpox virus serpin CrmA is necessary but not sufficient for the red pock phenotype on chicken chorioallantoic membranes

It was previously reported that cowpox virus (CPXV) strain Brighton Red (BR) causes red pocks upon inoculation of chorioallantoic membranes (CAMs) of embryonated chicken eggs. Red pocks are characterized by hemorrhage and reduced numbers of inflammatory cells while white pocks induced by other members of the genus Orthopoxvirus lack hemorrhage and have higher numbers of infiltrating heterophils. Analyses of CPXV BR white pock variants identified the cytokine response modifier A (CrmA) as the factor responsible for the differences in pock phenotype through induction of hemorrhage and inhibition of chemotaxis. In the present study CPXV crmA deletion mutants were generated based on a full-length bacterial artificial chromosome clone of CPXV BR (pBR). Deletion of the first crmA start codon was sufficient to abolish protein expression, whereas modification of a potential second start codon had no impact on CrmA production as shown by Western blot analysis. Immunohistochemistry of CAMs inoculated with crmA-positive BR viruses showed accumulation of viral antigen in endothelial cells, which was consistent with the red pock phenotype. On the other hand, crmA-negative mutants were characterized by the induction of white pocks and the absence of CPXV antigen in endothelia. The introduction of the complete CPXV BR crmA gene into the homologous genome region of the attenuated vaccinia virus strain MVA (modified vaccinia virus Ankara), however, resulted in CrmA production but not the red pock phenotype. We therefore conclude that (i) CPXV CrmA is associated with increased accumulation of virus in endothelial cells and (ii) the poxvirus-encoded serpin is necessary but not sufficient for the red pock phenotype and the anti-chemotactic capabilities on CAMs.     

Vessel density in OCT angiography permits differentiation between normal and glaucomatous optic nerve heads

AIM: To evaluate whether optical coherence tomography angiography (OCTA) can detect altered vessel density (VD) at the optic nerve head (ONH) in glaucoma patients. Special attention is paid to the accuracy of the OCTA technique for distinguishing healthy from glaucomatous eyes. METHODS: A total of 171 eyes were examined by the OCTA system AngioVue? (Optovue): 97 eyes diagnosed with glaucoma and 74 healthy control eyes. The papillary and peripapillary VD was measured. Furthermore, the VD was correlated with different structural and functional measurements. In order to test the accuracy of differentiation between eyes with and without glaucoma, we calculated the receiver operating characteristic curve (ROC) and the area under the curve (AUC). RESULTS: The papillary and peripapillary VD in glaucomatous eyes was significantly lower than in healthy eyes (P<0.05). The VD of the nasal peripapillary sector was significantly lower than in the other sectors. The further the disease had progressed [measured by determining the thickness of the ganglion cell complex (GCC) and the retinal nerve fiber layer (RNFL)] the greater the VD reduction. The AUC discriminated well between glaucomatous and normal eyes (consensus classifier 94.2%). CONCLUSION: OCTA allows non-invasive quantification of the peripapillary and papillary VD, which is significantly reduced in glaucomatous eyes and accurately distinguishes between healthy and diseased eyes. OCTA expands the spectrum of procedures for detecting and monitoring glaucoma.