Influence of biomass production and detachment forces on biofilm structures in a biofilm airlift suspension reactor

The influence of process conditions (substrate loading rate and detachment force) on the structure of biofilms grown on basalt particles in a Biofilm Airlift Suspension (BAS) reactor was studied. The structure of the biofilms (density, surface shape, and thickness) and microbial characteristics (biomass yield) were investigated at substrate loading rates of 5, 10, 15, and 20 kg COD/m3. day with basalt concentrations of 60 g/L, 150 g/L, and 250 g/L. The basalt concentration determines the number of biofilm particles in steady state, which is the main determining factor for the biofilm detachment in these systems. In total, 12 experimental runs were performed. A high biofilm density (up to 67 g/L) and a high biomass concentration was observed at high detachment forces. The higher biomass content is associated with a lower biomass substrate loading rate and therefore with a lower biomass yield (from 0.4 down to 0.12 gbiomass/gacetate). Contrary to general beliefs, the observed biomass detachment decreased with increasing detachment force. In addition, smoother (fewer protuberances), denser and thinner compact biofilms were obtained when the biomass surface production rate decreased and/or the detachment force increased. These observations confirmed a hypothesis, postulated earlier by Van Loosdrecht et al. (1995b), that the balance between biofilm substrate surface loading (proportional to biomass surface production rate, when biomass yield is constant) and detachment force determines the biofilm structure. When detachment forces are relatively high only a patchy biofilm will develop, whereas at low detachment forces, the biofilm becomes highly heterogeneous with many pores and protuberances. With the right balance, smooth, dense and stable biofilms can be obtained. Copyright 1998 John Wiley & Sons, Inc.     

Partially Folded Conformations of Inositol Monophosphatase Endowed with Catalytic Activity

The stability of porcine brain inositol monophosphatase in the presence of increasing concentrations of urea was investigated at pH 7.5. Exposure of the enzyme to 8 M urea brings about the dissociation of the dimeric species of 58 kDa into monomeric forms as revealed by gel filtration chromatography. Unfolding of the protein by 8 M urea results in a decrease of the ellipticity at 220 nm (20%) together with a perturbation of the near-UV circular dichroism spectrum. Urea-treated inositol monophosphatase binds Co²⁺ ions with a dissociation constant of 3.3 M. The enzyme is catalytically competent when assayed with 4-nitrophenyl-phosphate in the presence of the activating ion Co²⁺ at pH 7.5 in 8 M urea. The apparent activation constant for Co²⁺ is 2.5 mM. It is postulated that partially folded conformations of monomeric species preserve their catalytic function because the affinity of Co²⁺ ions for the metal coordination center of the protein is not perturbed by exposure to 8 M urea.     

Expression of GABA transaminase immunoreactivity in interneurons of the rat neostriatum

Immunoreactivity for γ-aminobutyric acid transaminase (GABA-T), a degradation enzyme for GABA, was localized by immunocytochemistry in the rat neostriatum and the globus pallidus using a monoclonal antibody. Immunoreactivity for GABA-T was found primarily in interneurons and in the neuropilar elements in the neostriatum. Many of GABA-T-immunoreactive neurons were found to display parvalbumin immunoreactivity. This indicates many of the GABA-T-immunoreactive neurons are striatal GABAergic interneurons. Occasionally, GABA-T-immunoreactive glial cells were found. In the globus pallidus, many pallidal neurons also displayed GABA-T immunoreactivity and many of the immunoreactive neurons were seen to express parvalbumin immunoreactivity. Immunoreactivity for GABA-T was also detected in the neuropil of the globus pallidus. The present results indicate the GABAergic interneurons in the neostriatum and a subpopulation of pallidal neurons play an important role in metabolic degradation of GABA in the basal ganglia.     

Prevalence of antibodies to Neospora caninum in horses in North America

Serum samples from 296 horses slaughtered for food in the United States were tested for antibodies to Neospora caninum by the Neospora-agglutination test (NAT). Antibodies were found in 69 (23.3%) horses with titers of 1:40 (19 horses), 1:80 (19 horses), 1:100 (3 horses), 1:200 (7 horses), 1:400 (4 horses), and 1:800 (17 horses). This is the first serologic survey for N. caninum antibodies in horses.     

A semiparametric joint model for cluster size and subunit-specific interval-censored outcomes

Clustered data frequently arise in biomedical studies, where observations, or subunits, measured within a cluster are associated. The cluster size is said to be informative, if the outcome variable is associated with the number of subunits in a cluster. In most existing work, the informative cluster size issue is handled by marginal approaches based on within-cluster resampling, or cluster-weighted generalized estimating equations. Although these approaches yield consistent estimation of the marginal models, they do not allow estimation of within-cluster associations and are generally inefficient. In this paper, we propose a semiparametric joint model for clustered interval-censored event time data with informative cluster size. We use a random effect to account for the association among event times of the same cluster as well as the association between event times and the cluster size. For estimation, we propose a sieve maximum likelihood approach and devise a computationally-efficient expectation-maximization algorithm for implementation. The estimators are shown to be strongly consistent, with the Euclidean components being asymptotically normal and achieving semiparametric efficiency. Extensive simulation studies are conducted to evaluate the finite-sample performance, efficiency and robustness of the proposed method. We also illustrate our method via application to a motivating periodontal disease dataset.     

Dosage effects for superoxide dismutase-1 in nucleated cells aneuploid for chromosome 21.

Assays of the activity of chromosome 21 determined superoxide dismutase-1 (SOD-1) in lymphocytes and polymorphonuclear granulocytes have demonstrated 38% and 40% increases, respectively, in cells from individuals with trisomy 21. Similarly, SOD-1 activity in trisomic fibroblasts is increased by 81%, while cells monosomic for chromosome 21 have only 60% of normal activity. Taken together with the data on SOD-1 activities in trisomic erythrocytes and platelets, the present results firmly confirm the existence of a true dosage effect for this enzyme in cells aneuploid for chromosome 21. However, the results of assays of the activity of glutathione peroxidase in trisomic fibroblasts did not confirm the possibility previously reported of a chromosome 21 related dosage effect for this enzyme.     

EFFECTS OF HYPOXIA ON TYROSINE HYDROXYLASE ACTIVITY IN RAT CAROTID BODY

Abstract— Tyrosine hydroxylase (TH) activity was measured in the carotid body. superior cervical ganglion and adrenal glands of the rat under normal conditions and at 48 h following exposure of the animals for 1-3 h in a low O₂ atmosphere. Basal TH levels were 5-6 nmol/h/mg tissue for both the carotid body and the ganglion. Forty-eight hours after hypoxia, there was an increase in enzyme activity in both tissues which paralleled the severity of the hypoxia but was greater in the carotid body than the superior cervical ganglion. Thus, following exposure to 5% O₂ in N₂ for two 30-min periods (20-min interim), TH activity had increased by 50% in the carotid body and 33% in the ganglion; after exposure to 10% O₂ in N₂ for 3 h (continuous), TH levels were increased by 37% in the carotid body and 12% in the ganglion. In the adrenal gland, basal TH activity was 3.42 ± 1.87 nmol/h/mg tissue, and this value was unchanged following either level of hypoxia.     

Mitochondrial UCP4 attenuates MPP+- and dopamine-induced oxidative stress,mitochondrial depolarization,and ATP deficiency in neurons and is interlinked with UCP2 expression

Mitochondrial uncoupling proteins (UCPs) uncouple oxidative phosphorylation from ATP synthesis. We explored the neuroprotective role of UCP4 with its stable overexpression in SH-SY5Y cells, after exposure to either MPP⁺ or dopamine to induce ATP deficiency and oxidative stress. Cells overexpressing UCP4 proliferated faster in normal cultures and after exposure to MPP⁺ and dopamine. Differentiated UCP4-overexpressing cells survived better when exposed to MPP⁺ with decreased LDH release. Contrary to the mild uncoupling hypothesis, UCP4 overexpression resulted in increased absolute ATP levels (with ADP/ATP ratios similar to those of controls under normal conditions and ADP supplementation) associated with increased respiration rate. Under MPP⁺ toxicity, UCP4 overexpression preserved ATP levels and mitochondrial membrane potential (MMP) and reduced oxidative stress; the preserved ATP level was not due to increased glycolysis. Under MPP⁺ toxicity, the induction of UCP2 expression in vector controls was absent in UCP4-overexpressing cells, suggesting that UCP4 may compensate for UCP2 expression. UCP4 function does not seem to adhere to the mild uncoupling hypothesis in its neuroprotective mechanisms under oxidative stress and ATP deficiency. UCP4 overexpression increases cell survival by inducing oxidative phosphorylation, preserving ATP synthesis and MMP, and reducing oxidative stress.     

Evaluation using multilayer perception neural networks: a case study of undulatory median fin swimming in the knifefish Xenomystus nigri

In this study, artificial intelligence, namely multilayer perception neural networks (MLP-NN), was employed to predict the hydrodynamic performance of undulatory median fin propulsion in Xenomystus nigri . Good agreement was found between MLP-NN predictions and actual mean thrust and power values calculated from elongated-body theory. MLP-NN has the ability to be a predictive tool for autonomous underwater vehicle design and hydrodynamic performance.