Modeling microalgal flocculation and sedimentation

In this study, a combined flocculation and sedimentation model is developed. The model predicts the time needed to reach a desired concentration of microalgal suspension in a sedimentation tank. The concentration of the particles as function of the time and the position in the tank is described. The model was validated with experimental data for Ettlia texensis. The concentration changes measured in time at different heights in the sedimentation vessel corresponded well with model predictions. The model predicts that it takes 25 h to reach a final concentration of 5.2 gDW L(-1), when the initial concentration is 0.26 gDW L(-1) and the tank height is 1m. This example illustrates the use of this model for the design of the settling tank needed for pre-concentration of microalgal biomass before further dewatering.

Effect of growth phase on harvesting characteristics, autoflocculation and lipid content of Ettlia texensis for microalgal biodiesel production

The effect of growth phase on the recovery of the autoflocculating microalgae Ettlia texensis was studied. In the stationary phase, 90% recovery was achieved after 3h settling. Scanning electron microscopic pictures revealed that extracellular polymeric substances (EPS) on the cell surface were involved in autoflocculation. During the stationary phase an increase of the protein fraction in the EPS was observed while the total fatty acids content increased. The autoflocculating properties of E. texensis combined with favourite fatty acid content and composition make this microalgae an excellent candidate for biodiesel production if harvested at the end of the stationary phase.

Ratio between autoflocculating and target microalgae affects the energy-efficient harvesting by bio-flocculation

The effect of ratio between autoflocculating and target microalgae in bio-flocculation was studied with emphasis on the recovery, sedimentation rate and energy demand for harvesting the target microalgae. When the autoflocculating microalgae Ettlia texensis, Ankistrodesmus falcatus and Scenedesmus obliquus were added to Chlorella vulgaris at a ratio of 0.25, the recovery of C. vulgaris increased from 25% to, respectively, 40%, 36% and 31%. The sedimentation rate increased as well. Addition of Tetraselmis suecica to Neochloris oleoabundans at a ratio of 0.25 increased the recovery from 40% to 50%. Application of bio-flocculation at a ratio of 0.25, followed by centrifugation reduces the energy demand for harvesting of the target microalgae from 13.8 MJ kgDW(-1) if only centrifugation is used to 1.83, 1.81, 1.53 and 1.34 MJ kgDW(-1), respectively, using T. suecica, E. texensis, A. falcatus and S. obliquus and 3h sedimentation before centrifugation.

Chronic adrenaline treatment fails to down-regulate the Del301-303-alpha2B-adrenoceptor in neuronal cells

BACKGROUND AND PURPOSE

A polymorphism of the human alpha(2B)-adrenoceptor (Del(301-303)-alpha(2B)-adrenoceptor) has been described, and this receptor exhibits reduced G-protein-coupled receptor kinase (GRK) phosphorylation and impaired short-term desensitization. Expression of the Del(301-303)-alpha(2B)-adrenoceptor also is associated with an increased risk for myocardial infarction in humans. Recent evidence from our laboratory suggests a quantitative relationship between cellular GRK3 expression levels and the sensitivity of the alpha(2B)-adrenoceptor to agonist-induced down-regulation. Therefore, the present study was undertaken to study agonist-induced down-regulation of the wild-type (WT)- and Del(301-303)-alpha(2B)-adrenoceptor in a neuronal cell model.

EXPERIMENTAL APPROACH

Haemagglutinin (HA) epitope-tagged WT- and Del(301-303)-alpha(2B)-adrenoceptor containing plasmids were constructed and the receptors were stably or transiently transfected in neuroblastoma/glioma hybrid NG108 cells. The expression levels in stable transfects were approximately 50 fmol x mg(-1). These cells were used to examine agonist-induced down-regulation and phosphorylation of the WT- and Del(301-303)-alpha(2B)-adrenoceptor.

KEY RESULTS

The Del(301-303)-alpha(2B)-adrenoceptor, compared with the WT-alpha(2B-)adrenoceptor, displayed reduced adrenaline-stimulated (20 microM) phosphorylation and did not down-regulate in response to adrenaline (20-1000 microM). Using immunofluorescence labelling, we observed that transiently transfected WT-alpha(2B)-adrenoceptors internalized upon adrenaline treatment whereas the Del(301-303)-alpha(2B)-adrenoceptor did not. Finally, we determined the effect of adrenaline on the Del(301-303)-alpha(2B)-adrenoceptor in cells stably over-expressing GRK3 3-fold. In spite of the GRK3 over-expression, 20-1000 microM ADR failed to down-regulate or to increase phosphorylation of the Del(301-303)-alpha(2B)-adrenoceptor in these cells.

CONCLUSIONS AND IMPLICATIONS

The results suggest that the 301-303 deletion mutation of the alpha(2B)-adrenoceptor eliminates agonist-induced down-regulation, an effect that cannot be overcome by increasing agonist concentration or by modest GRK3 over-expression.

Trabeculectomy and optic nerve head topography

The objective of the present study was to evaluate changes in optic nerve head parameters, measured by confocal laser tomography, before and after trabeculectomy in order to identify outcome measures for the management of glaucoma. The optic nerve head of 22 eyes (22 patients) was analyzed by confocal laser tomography with the Heidelberg retinal tomogram (HRT) before and after trabeculectomy. The median time between the first HRT and surgery was 4.6 months (mean: 7.7 +/- 8.3) and the median time between surgery and the second HRT was 10.8 months (mean: 12.0 +/- 6.8). The patients were divided into two groups, i.e., those with the highest (group A) and lowest (group B) intraocular pressure (IOP) change after surgery. Differences in the 12 standard topographic parameters before and after surgery for each group were evaluated by the Wilcoxon signed rank test and the differences in these parameters between the two groups were compared by the Mann-Whitney rank sum test. Multiple regression analysis was used to evaluate the influence of the change in IOP (DeltaIOP and DeltaIOP%) and the changes in the other parameters. There were significant differences in the HRT measures before and after surgery in group A only for cup volume. In group B, no parameter was statistically different. The changes in group A were not significantly different than those in group B for any parameter (P > 0.004, Bonferroni correction for multiple comparisons). DeltaIOP and DeltaIOP% had a statistically significant effect on Delta cup disk area, Delta cup volume and Delta mean cup depth. Changes in cup shape size were influenced significantly only by DeltaIOP. Some optic disc parameters measured by HRT presented a significant improvement after filtering surgery, depending on the amount of IOP reduction. Long-term studies are needed to determine the usefulness of these findings as outcome measures in the management of glaucoma.

Influence of surgical reduction of intraocular pressure on regions of the visual field with different levels of sensitivity

PURPOSE

To determine whether the ability to document improvement in visual fields after intraocular pressure (IOP) reduction can be enhanced by focusing on regions of the field with different levels of sensitivity.

DESIGN

Cohort study.

METHODS

This is a retrospective study.

SETTING

Yale Eye Center.

STUDY POPULATION

The visual fields (Octopus G2) of 30 eyes of 30 patients undergoing trabeculectomy.

OBSERVATION PROCEDURE

Visual fields were evaluated a mean of three months before and 7.8 months after surgery.

MAIN OUTCOME MEASURES

Change in sensitivity between the preoperative and postoperative visual fields (Delta S) was evaluated globally by comparing all 59 points of sensitivity and regionally in three groups according to preoperative sensitivity (pre-S): 25% of highest, 50% intermediate, and 25% of lowest points of sensitivity. Improvement in Delta S was also correlated with preoperative mean defect (pre-MD), percent intraocular pressure (IOP) reduction (Delta IOP%), and patient's age.

RESULTS

Six visual fields showed improvement in Delta S when evaluated globally and nine showed improvement in pre-S subgroups. Of the latter, all nine showed improvement in the subgroup with the lowest pre-S, and two in the intermediate subgroup, but none in the subgroup with the highest pre-S. Combining the subgroups with the lowest pre-S and the highest Delta IOP% was associated with the highest mean Delta S.

CONCLUSION

The ability to document improvement in visual fields following surgical reduction of IOP may be enhanced by focusing on subgroups of test points with lower baseline sensitivity.

Visually significant cystoid macular edema in pseudophakic and aphakic patients with glaucoma receiving latanoprost

PURPOSE

To investigate the incidence of visually significant cystoid macular edema associated with the use of latanoprost in patients with glaucoma after cataract surgery.

PATIENTS AND METHODS

This is a multicenter, retrospective study of 185 patients, of whom 173 were pseudophakic (212 eyes) and 12 were aphakic (13 eyes), who were treated for glaucoma with latanoprost 0.005%. The posterior lens capsule was intact in 125 eyes, open or absent as a result of surgery in 25 eyes, and status-post-yttrium-aluminum-garnet capsulotomy in 75 eyes. Visual acuity was documented before and after initiating latanoprost therapy, and patients with a reduction of two or more lines on the Snellen chart were examined by fluorescein angiography for cystoid macular edema.

RESULTS

Visual reduction was documented in four (2.16%) patients. Three of the four patients had cystoid macular edema, and the fourth was thought to have lost a central island of vision from glaucoma. The three patients with cystoid macular edema all had ruptured posterior capsules, requiring anterior vitrectomy, and one had a previous episode of cystoid macular edema 3 years before starting latanoprost therapy.

CONCLUSION

These findings suggest that visually significant cystoid macular edema associated with latanoprost therapy in pseudophakic or aphakic patients is uncommon. If there is a cause-and-effect relationship between latanoprost therapy and clinically significant cystoid macular edema, the incidence appears to be low.

Hepatitis B vaccination among health care workers and students of a medical college

OBJECTIVE

To study the vaccination status against Hepatitis B among health care workers and students of a medical school.

MATERIALS AND METHODS

It is a descriptive study done at Allama Iqbal Medical College, Lahore. The participants comprised of 206 health care workers of various categories and 327 medical students. The main outcome measure was vaccination status and reasons for non-vaccination.

RESULTS

Only 49% health care workers and 42.20% medical students were vaccinated. The main reasons for non-vaccination (47.7%) among health care workers was the high cost of vaccination, while the most often cited reason (33.7%) among medical student was the belief that they were not at risk. This belief was also prevalent among nurses (36.4%), laboratory workers (38.6%) and paramedics (33.2%).

CONCLUSION

In a low-income country like Pakistan the health institutions should bear the cost for vaccinating their staff. Efforts should also be made to impart appropriate health education regarding hepatitis B infection.

Lack of quinone reductase activity suggests that amyloid-beta peptide/ERAB induced lipid peroxidation is not directly related to production of reactive oxygen species by redoxcycling

Mitochondrial type II hydroxyacyl-CoA dehydrogenase (ERAB) has recently been shown to mediate amyloid-beta peptide (Abeta) induced apoptosis and neurodegeneration. The precise mechanism of cell death induction is unknown, however, Abeta inhibits ERAB activities and as a result of ERAB-Abeta interactions, enhanced formation of lipid peroxidation products occur. The possibility that ERAB mediates quinone reduction is therefore investigated, thus giving the potential of redoxcycling and production of reactive oxygen species, leading to lipid peroxidation. Recombinant human ERAB was produced in a bacterial expression system and enzymological properties were evaluated. Using several orthoquinones as substrates, no ERAB mediated quinone reductase activity was found either in the presence or absence of Abeta, suggesting that the observed in vivo lipid peroxidation is a result of other mechanisms than redoxcycling by quinones.

Binding of amyloid beta-peptide to mitochondrial hydroxyacyl-CoA dehydrogenase (ERAB): regulation of an SDR enzyme activity with implications for apoptosis in Alzheimer's disease

The intracellular amyloid beta-peptide (A beta) binding protein, ERAB, a member of the short-chain dehydrogenase/reductase (SDR) family, is known to mediate apoptosis in different cell lines and to be a class II hydroxyacyl-CoA dehydrogenase. The A beta peptide inhibits the enzymatic reaction in a mixed type fashion with a Ki of 1.2 micromol/l and a KiES of 0.3 micromol/l, using 3-hydroxybutyryl-CoA. The peptide region necessary for inhibition comprises residues 12-24 of A beta1-40, covering the 16-20 fragment, which is the minimum sequence for the blockade of A beta polymerization, but that minimal fragment is not sufficient for more than marginal inhibition. The localization of ERAB to the endoplasmic reticulum and mitochondria suggests a complex interaction with components of the programmed cell death machinery. The interaction of A beta with ERAB further links oxidoreductase activity with both apoptosis and amyloid toxicity.

Effect of reversible and irreversible ischemia on marker enzymes of BBM from renal cortical PT subpopulations

The effect of the reversible and relatively irreversible ischemia induced acute renal failure (ARF) in the activities of alkaline phosphatase (AlkPase) and gamma-glutamyltransferase (GGTase) after early (15-30 min) and prolonged (45-60 min) ischemia in the homogenates, and the brush-border membranes (BBM) from rat renal whole, superficial (SC), and juxtamedullary (JMC) cortices were studied. The enzyme activities declined progressively in proportion to the duration of ischemia. Early blood reflow of 15 min to the ischemic rats caused a further decrease in the enzyme activities. However, prolonged reflow (up to 120 min) resulted in partial reversal of the ischemic effect in the early but not in the prolonged ischemic rats. The decrease in the enzyme activities was due to the loss of membrane-bound enzyme components from the damaged BBM into the supernatant fraction as membrane-free enzymes. The activities of AlkPase and GGTase were significantly more decreased by the ischemia in the brush-border membrane vesicles (BBMV)-JMC than in BBMV-SC. The rate of recovery due to reflow for AlkPase was greater in BBMV-SC than apparently for GGTase in BBMV-JMC in early ischemic (15-30 min) rats.

Videothoracoscopic ligation of patent ductus arteriosus--a case report

Video-assisted thoracoscopic surgical interruption (VTSI) of patent ductus arteriosus (PDA) is a relatively new technique when compared to surgical closure and transcatheter endovascular closure. Besides its minimally invasive nature, VTSI is the best option for neonates. Surgical approach may lead to late scoliosis in neonates and the vessels of neonates are too small for the transcatheter approach. VTSI potentially may prove to have lower morbidity and mortality than classic surgical closure of PDA. This article reviews the successful videothoracoscopic ligation of PDA in a 13-year-old girl.

Non-Hodgkins lymphoma presenting as pure red cell aplasia

An interesting case of Non-Hodgkins lymphoma presenting as pure red cell aplasia is being reported. Even though acquired pure red cell aplasia is not uncommon, lymphoma presenting as pure red cell aplasia is very rare. The patient responded to COP treatment and red cell transfusion and is on regular follow up. This appears to be the first report of such an association in Indian literature.

Chicken pox induced pancytopenia and prompt response to high dose intravenous immunoglobulin

This is to highlight the rare complication of pancytopenia following an attack of chickenpox and the favourable response to high dose intravenous immunoglobulin. We are hereby postulating the cause of this refractory pancytopenia as viral antibody mediated event and hence the response to intravenous immunoglobulin.

The dimensional accuracy of rectangular acrylic resin specimens cured by three denture base processing methods

The dimensional accuracy of rectangular acrylic resin specimens was examined when they were processed by three methods: a conventional method, the SR-Ivocap system, and a microwave curing method. The dimensional accuracy was evaluated by the change of the distance vector V, which is calculated by means of measurements of the distances between fixed points on specimens. The specimen cured by the SR-Ivocap system exhibited less dimensional change (p less than 0.05) than those cured by the conventional and the microwave curing methods. The SR-Ivocap system might produce a more accurate denture base than the conventional and the microwave curing methods.

Antiphospholipid antibody syndrome of systemic lupus erythematosus presenting as deep vein thrombosis

We are reporting a young lady with protracted deep vein thrombosis of her left leg which turned out to be antiphospholipid (anticardiolipin) antibody syndrome of ANA positive systemic lupus erythematosus. Lupus anticoagulant was demonstrated by prolongation of activated partial thromboplastin time and Russell's viper venom time. She had no anti-thrombin III deficiency.