Analysis of retinal circulation using an image-based network model of retinal vasculature

This paper presents the results of a circulation analysis using an image based network model of a murine retinal vasculature, which closely represents the 3D vascular distribution of the retina. The uneven distribution of the red blood cells at vascular network bifurcations (i.e., plasma skimming effect), the microvascular diameter effect (i.e., Fahraeus-Lindqvist effect) and the role of endothelium surface layer (i.e., in vivo viscosity) were considered in determining the viscosity of the blood in the retinal vessel segments. The study yielded detailed distributions of the hemodynamic quantities in the arterial and venous trees shown in various anatomical based contour plots. Quantitative analysis was also carried out based on statistical distributions. The analysis shows that the distribution of the blood hematocrit (H(D)) in the retinal network is very non-uniform, with lower values at the pre-equator region (near the optic disc) and higher values in the equator region of the retina. This has significant influence on the distribution of apparent viscosity, pressure and wall shear stress (WSS) in the vasculature. The viscosity is generally higher in smaller vessels (i.e., pre-capillary vessels) but exceptions occur in some vessels where the H(D) is small. WSS is greater in smaller vessels located near the optic disc than that in the mainstream retinal vessels. The results presented can be directly useful to ophthalmologists and researchers working with retinal vasculature.

Effect of chloride concentration on nitrogen removal from landfill leachate in sequencing batch reactor after MAP pretreatment

Leachate generated from landfill is becoming a great environmental challenge to China as it contains high concentration of COD, ammonium and some other substances. Nitrogen removal through the conventional nitrification-denitrification process is hampered by the low C/N ratio especially for the old age landfill sites and the high energy consumption for aeration. In this study, the combination of magnesium ammonium phosphate (MAP) precipitation and Sequencing batch reactor (SBR) was suggested as a new process for the treatment of high strength ammonium, and the effect of high concentration of Cl⁻ after MAP precipitation because of the use of MgCl₂ was investigated on SBR performance. The practical upper limit of Cl⁻ for nitrification was found to be 12,000 mg/L, above which resulted in significant accumulation of ammonium in SBR system. It is suggested that an ammonium removal of 70% was suitable for the MAP treatment to achieve a balance between increasing the C/N ratio and avoiding detrimental effect from high concentration of Cl⁻ in the succeeding SBR system. DGGE analysis indicated that high diversity of Ammonium oxidizing bacteria (AOB) could be maintained at a Cl⁻ concentration of 12,000 mg/L.

The uplift of Qinghai-Xizang (Tibet) Plateau and the vicariance speciation of glyptosternoid fishes (Siluriformes: Sisoridae)

Based on the phylogenetic and biogeographical studies of the glyptosternoid fishes in Qinghai-Tibet area, the following hypothesis is proposed: the speciation of this group has a direct relationship with the three uplift intervals of the Qinghai-Tibet Plateau. This process was explained by the theory of vicariance of biogeography. The ancestor of this group was similar to Bagarus and/or Glyptothorax, which still have a wide distribution. At the moment when the Tethys sea closed, the Indian tectonic plate collided with the Eurasian tectonic plate, so the Glyptothorax-like and Bagarus-like ancestors entered Eurasia and gradually became widely distributed. After the Pleistocene, with the enforced colliding, the gradual uplift of the Qinghai-Tibet Plateau brought about the current water environment, and the Glyptosternoids were generated from Glyptothorax-like fish under this environment. The present Glyptosternum, distributed across the Himalayas is the ancestor of Glyptosternoids. In the three uplift intervals of the plateau, the water system of this region was separated gradually and Glyptosternum-like ancestor was isolated in different rivers and evolved into various species. All this resulted in the speciation and formation of the biogeographical pattern of glyptosternoids.

Deterministic Dynamics in Neuronal Discharge from Pallidotomy Targets

The non-linear dynamic specificity of the firing pattern discharged from neurons of the internal globus pallidus (GPi) was investigated by recording their spontaneous firing using a microelectrode during posteroventral pallidotomy in eight patients with Parkinson's disease. Raw data from the cells were processed to extract spiking events (discharges above a selected threshold) and the interspike interval was measured. Using the unstable periodic orbits extraction method, significant period-1, −2 and −3 orbits were identified in burst firing discharged from the GPi cells in all eight patients, suggesting that deterministic dynamics exist in the timing of the discharges. As well as providing a useful peri-operative technique for locating posteroventral pallidotomy targets in Parkinson's disease, this method also provides a promising basis for investigating characteristic neuronal discharges in other regions of the brain and for various other neurological disorders.

Induction of T-helper type 2 cytokine release and up-regulated expression of protease-activated receptors on mast cells by recombinant American cockroach allergen Per a 7

BACKGROUND

The cockroach is a major source of indoor allergens, which cause perennial rhinitis and asthma. Per a 7 is one of the major allergens from the American cockroach, eliciting IgE reaction in over 50% of sera from allergic individuals. However, the actions of Per a 7 in the pathogenesis of allergic diseases remain poorly understood.

OBJECTIVE

The aim of the study was to investigate the effects of Per a 7 on the expression of protease-activated receptors (PARs) on murine mast cells and the release of T-helper type 2 (Th2) cytokines from these cells. Methods Per a 7 gene was cloned and expressed in Escherichia coli. The purified recombinant Per a 7 (rPer a 7) was used to challenge murine mast cells P815 and the expression of PARs was determined by using real-time quantitative RT-PCR and flow cytometry. The release of IL-4 and IL-13 was detected with ELISA.

RESULTS

rPer a 7 was solubly expressed in E. coli and the purified rPer a 7 reacted with 75% (six out of eight) of the sera from cockroach-allergic patients. Following stimulation of rPer a 7, the expression of PAR-1, PAR-2, PAR-3 and PAR-4 mRNAs on P815 cells increased by 8.7-, 6.8-, 14.4- and 8.8-fold, respectively, following 2- and 6-h incubation periods, and the expression of PAR-1, PAR-2 and PAR-4 proteins was enhanced following 16-h incubation. rPer a 7 provoked approximately up to a 4.8- and 2.3-fold increase in IL-4 and IL-13 release from P815 cells following 6- and 16-h incubation periods.

CONCLUSION

rPer a 7 induced up-regulation of PAR expression on P815 cells and provoked Th2 cytokines IL-4 and IL-13 secretion from these murine mast cells, which implicated that this major cockroach allergen is likely to contribute to the development of cockroach-related allergic disease.

Two distinct conformations of the conserved RNA-rich decoding center of the small ribosomal subunit are recognized by tRNAs and release factors

The mRNA is bound and poised in the decoding center of the small subunit of the ribosome where the genetic code is translated by the tRNAs, which recognize sense codons, and by the release factors, which recognize stop-codons. Structural and biochemical studies have identified key universally conserved nucleotides, G530, A1492, and A1493, that are important for selection of cognate tRNA species during elongation. Here, we present evidence that these same universally conserved nucleotides are also important for interactions with the release factors, but must assume a very different structure during stopcodon recognition. These data provide mechanistic insight into how the decoding center of the ribosome has evolved to recognize distinct substrates with high fidelity, which in turn regulates the downstream chemical events of peptidyl transfer and peptide release.

The taxane-enhancer STA-4783 induces Hsp70 expression and apoptosis via an oxidative stress mechanism

14107

Background: STA-4783 is an inducer of Hsp70 expression and apoptosis that recently completed a successful Phase II clinical trial in melanoma. In a double-blind, randomized, controlled trial in patients with Stage IV disease, STA-4783 plus paclitaxel doubled progression-free survival compared to paclitaxel alone (Perspectives in Melanoma X and the Third International Melanoma Research Congress, 2006). The mechanism by which STA-4783 synergizes with paclitaxel is not fully understood. To identify the major pathway modulated by STA- 4783 in vitro, a transcriptional profiling analysis of drug-treated melanoma cells was performed. Methods: Transcriptional profiling was performed on Hs294T and MDA-MB-435 melanoma cell lines treated with STA-4783. The induction of Hsp70 RNA and other human genes was monitored by Real Time-PCR (RT-PCR) analysis. Measurement of reactive oxygen species (ROS) was performed in human cells using the Carboxy-H2DCFDA probe. Levels of apoptotic cell death were determined by flow cytometry analysis using an Annexin V specific probe. Results: Transcriptional profiling revealed that STA-4783 induced the expression of numerous gene families known to be regulated by oxidative stress, including heat shock proteins and metallothioneins. STA-4783 induced the generation of ROS in cells resulting in the oxidation and activation of the Carboxy-H2DCFDA fluorescent probe. The antioxidants N-Acetyl Cysteine (NAC) and Tiron potently blocked the induction of Hsp70 RNA and apoptotic cell death. Conclusions: STA-4783 induces oxidative stress in cells resulting in Hsp70 induction and apoptotic cell death. Although STA-4783 initially induced a transient protective response, apoptotic cell death occurred due to sustained oxidative stress. Cancer cells produce more ROS than normal cells and are thus more sensitive to insults that induce oxidative stress. The induction of ROS in melanoma cells by STA-4783 may therefore enhance the efficacy of paclitaxel in vivo. STA-4783 belongs to a novel class of anticancer agents that induce cell death by pushing the cancer cell beyond its oxidative stress breaking point.

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A rapid immunoassay to determine concentrations of busulfan in plasma

7111

Background: High-dose busulfan is an important component of many bone marrow transplantation preparative regimens. High busulfan plasma levels have been shown to increase the chance of veno-occlusive disease and low levels are associated with recurrence of disease or graph rejection. Currently, busulfan levels are monitored by physical methods which are expensive and time- consuming, resulting in relatively low overall use of busulfan testing for dose adjustment. Methods: Novel, highly selective antibodies for busulfan have been generated and micro-titer plate immunoassays that are capable of quantifying busulfan levels in plasma have been developed. The assay was configured using a busulfan-horseradish peroxidase conjugate as the reporter group and busulfan monoclonal antibodies. The assay requires only 5 μL of plasma per determination with no sample preparation. Results: The immunoassay has a standard curve based on busulfan with a range of 75 to 2,000 ng/mL. The time to first result is 30 minutes with up to 240 tests generated per hour. The coefficient of variation (CV) on signal is < 5% for an entire plate and the 95% confidence interval for negative samples (n=78) is below the lowest calibrator of 75 ng/mL. Cross-reactivity with the major inactive metabolites (tetrahydrothiophene,tetramethyl sulfone and tetrahydrothiophene-3-ol-1,1-dioxide), are <0.1%. Clinical samples (n=70) correlate well to LC-MSMS or GC-MS (R > 0.97) with a slope of < 1.05. Conclusions: This immunoassay method may be suitable for determining levels of busulfan in human plasma. It offers the advantages of using a smaller sample size, does not require sample preparation and is less labor intensive than other methods. The ability to make 240 determinations per hour enables effective routine monitoring of busulfan levels in clinical practice.

No significant financial relationships to disclose.

Early onset vitreous amyloidosis in familial amyloidotic polyneuropathy with a transthyretin Glu54Gly mutation is associated with elevated vitreous VEGF

AIM

To report the early vitreous involvement in a rare familial amyloidotic polyneuropathy (FAP) mutation and associated vitreous vascular endothelial growth factor (VEGF) levels.

DESIGN

Observational case series.

METHODS

Review of clinical, pathological, photographic, and angiographic records of two FAP siblings with severe vitreous involvement. Laboratory ELISA analysis of vitreous samples for VEGF, and DNA sequence analysis of peripheral blood for transthyretin (TTR) mutational analysis.

RESULTS

Two patients underwent 25-gauge vitrectomy in three eyes with marked improvement of visual acuity. Neovascularisation seen intraoperatively responded to endolaser. Analysis of vitrectomy samples for VEGF showed raised levels in all three specimens. Mutational analysis revealed an isolated Glu54Gly mutation in the transthyretin gene.

CONCLUSIONS

Early involvement of the vitreous occurs in a rare transthyretin mutation of FAP, with increased vitreous levels of VEGF.