Characterization of partially purified catalase from camel (Camelus dromedarius) liver

The liver of camel has high level of catalase (32,225 units/g tissue) as commercially used bovine liver catalase. For the establishment of the enzyme, the rate of catalase activity was linearly increased with increase of the catalase concentration and incubation time. The procedure of partial purification of catalase from camel liver included preparation of crude extract, ammonium sulphate precipitation and chromatography on diethylaminoethyl cellulose (DEAE)-Sepharose. One peak catalase activity was obtained from the chromatography. The enzyme had optimum pH of 7.0. Camel liver catalase had broad optimum temperature between 25 and 40°C and was stable up to 25°C. The Km and Vmax values were found to be 22.7 mM H2O2/ml and 7.9 units/ml, respectively. All metal cations partially inhibited camel liver catalase with the exception of Hg2+ which had strong inhibitory effect, whereas 95% of its activity was lost at 1.0 mM. In conclusion, camel liver catalase can be used as an alternative commercial bovine liver catalase.Key words: Camel, liver, catalase, purification, characterization

The Classic Approach to Diagnosis of Vulvovaginitis: A Critical Analysis

Objective: To correlate the symptoms, signs and clinical diagnosis in women with vaginal discharge, based on the combined weight of the character of the vaginal discharge and bedside tests, with the laboratory diagnosis. Methods: Women presenting consecutively to the women's health center with vaginal discharge were interviewed and examined for assessment of the quantity and color of the discharge. One drop of the material was then examined for pH and the whiff test was done; a wet mount in saline and in 10% KOH was examined microscopically. The clinical diagnosis was based on the results of these assessments. Gram stain and cultures of the discharge were sent to the microbiology laboratory. Results: One hundred and fifty-threewomen with vaginal discharge with a clinical diagnosis of vulvovaginitis participated in the study. Fifty-five (35.9%) had normal flora and the other 98 (64.1%) had true infectious vulvovaginitis (k agreement = 18%). According to the laboratory, the principal infectious micro-organism causing the vulvovaginitis was Candida species. Candida infection was associated with pH levels of less than 4.5 (p < 0.0001, odds ratio = 4.74, 95% confidence interval: 2.35–9.5, positive predictive value 68.4%). The whiff test was positive in only a small percentage of bacterial vaginosis (BV) (p = not significant (NS)). Clue cells were documented in 53.3% of patients with a laboratory diagnosis of BV (p < 0.02, positive predictive value 26.7%). Conclusions: The current approach to the diagnosis of vulvovaginitis should be further studied. The classical and time-consuming assessments were shown not to be reliable diagnostic measures

Physiological and pathological aspects of Aβ in iron homeostasis via 5'UTR in the APP mRNA and the therapeutic use of iron-chelators

Many studies have highlighted the pathological involvement of iron accumulation and iron-related oxidative stress (OS) in Alzheimer's disease (AD). Iron was further demonstrated to modulate expression of the Alzheimer's amyloid precursor holo-protein (APP) by a mechanism similar to that of regulation of ferritin-L and -H mRNA translation through an iron-responsive element (IRE) in their 5' untranslated regions (UTRs). Here, we discuss two aspects of the link between iron and AD, in relation to the recently discovered IRE in the 5'UTR of APP mRNA. The first is the physiological aspect: a compensatory neuroprotective response of amyloid-β protein (Aβ) in reducing iron-induced neurotoxicity. Thus, given that Aβ possesses iron chelation sites, it is hypothesized that OS-induced intracellular iron may stimulate APP holo-protein translation (via the APP 5'UTR) and subsequently the generation of its cleavage product, Aβ, as a compensatory response that eventually reduces OS. The second is the pathological aspect: iron chelating compounds target the APP 5'UTR and possess the capacity to reduce APP translation, and subsequently Aβ levels, and thus represent molecules with high potential in the development of drugs for the treatment of AD

Identifying dynamical modules from genetic regulatory systems: applications to the segment polarity network

BACKGROUND It is widely accepted that genetic regulatory systems are 'modular', in that the whole system is made up of smaller 'subsystems' corresponding to specific biological functions. Most attempts to identify modules in genetic regulatory systems have relied on the topology of the underlying network. However, it is the temporal activity (dynamics) of genes and proteins that corresponds to biological functions, and hence it is dynamics that we focus on here for identifying subsystems. RESULTS Using Boolean network models as an exemplar, we present a new technique to identify subsystems, based on their dynamical properties. The main part of the method depends only on the stable dynamics (attractors) of the system, thus requiring no prior knowledge of the underlying network. However, knowledge of the logical relationships between the network components can be used to describe how each subsystem is regulated. To demonstrate its applicability to genetic regulatory systems, we apply the method to a model of the Drosophila segment polarity network, providing a detailed breakdown of the system. CONCLUSION We have designed a technique for decomposing any set of discrete-state, discrete-time attractors into subsystems. Having a suitable mathematical model also allows us to describe how each subsystem is regulated and how robust each subsystem is against perturbations. However, since the subsystems are found directly from the attractors, a mathematical model or underlying network topology is not necessarily required to identify them, potentially allowing the method to be applied directly to experimental expression data

Visual Search Strategies of Soccer Players Executing a Power vs. Placement Penalty Kick

Introduction: When taking a soccer penalty kick, there are two distinct kicking techniques that can be adopted; a ‘power’ penalty or a ‘placement’ penalty. The current study investigated how the type of penalty kick being taken affected the kicker’s visual search strategy and where the ball hit the goal (end ball location). Method: Wearing a portable eye tracker, 12 university footballers executed 2 power and placement penalty kicks, indoors, both with and without the presence of a goalkeeper. Video cameras were used to determine initial ball velocity and end ball location. Results: When taking the power penalty, the football was kicked significantly harder and more centrally in the goal compared to the placement penalty. During the power penalty, players fixated on the football for longer and more often at the goalkeeper (and by implication the middle of the goal), whereas in the placement penalty, fixated longer at the goal, specifically the edges. Findings remained consistent irrespective of goalkeeper presence. Discussion/conclusion: Findings indicate differences in visual search strategy and end ball location as a function of type of penalty kick. When taking the placement penalty, players fixated and kicked the football to the edges of the goal in an attempt to direct the ball to an area that the goalkeeper would have difficulty reaching and saving. Fixating significantly longer on the football when taking the power compared to placement penalty indicates a greater importance of obtaining visual information from the football. This can be attributed to ensuring accurate foot-to-ball contact and subsequent generation of ball velocity. Aligning gaze and kicking the football centrally in the goal when executing the power compared to placement penalty may have been a strategy to reduce the risk of kicking wide of the goal altogether

A Markov chain model for changes in users’ assessment of search results

Previous research shows that users tend to change their assessment of search results over time. This is a first study that investigates the factors and reasons for these changes, and describes a stochastic model of user behaviour that may explain these changes. In particular, we hypothesise that most of the changes are local, i.e. between results with similar or close relevance to the query, and thus belong to the same ”coarse” relevance category. According to the theory of coarse beliefs and categorical thinking, humans tend to divide the range of values under consideration into coarse categories, and are thus able to distinguish only between cross-category values but not within them. To test this hypothesis we conducted five experiments with about 120 subjects divided into 3 groups. Each student in every group was asked to rank and assign relevance scores to the same set of search results over two or three rounds, with a period of three to nine weeks between each round. The subjects of the last three-round experiment were then exposed to the differences in their judgements and were asked to explain them. We make use of a Markov chain model to measure change in users’ judgments between the different rounds. The Markov chain demonstrates that the changes converge, and that a majority of the changes are local to a neighbouring relevance category. We found that most of the subjects were satisfied with their changes, and did not perceive them as mistakes but rather as a legitimate phenomenon, since they believe that time has influenced their relevance assessment. Both our quantitative analysis and user comments support the hypothesis of the existence of coarse relevance categories resulting from categorical thinking in the context of user evaluation of search results

The Abnormal Contralateral Atrioventricular Valve in Mitral and Tricuspid Atresia in Neonates: An Echocardiographic Study

Abnormalities of the mitral valve (MV) or the tricuspid valve (TV) morphology and/or function in patients with functional single ventricle may result in early morbidity and death. The purpose of this study was to determine the incidence of contralateral atrioventricular valve (AVV) pathologies in mitral valve atresia (MA) and tricuspid valve atresia (TA). We retrospectively reviewed the echocardiographic data of 50 neonates with MV and 20 with TA. Appearance of the papillary muscles, chordae tendinae, and valve leaflets was assessed. AVV regurgitation was semiquantitated by color-flow Doppler and the AVV annulus diameter was measured and indexed to body surface area. MV abnormalities were found in 9 of 20 (45%) of patients with TA. The MV was myxomatous in 9 patients, the leaflets were redundant in 5 patients, and prolapsing occurred in 4 patients. Mild regurgitation was found in 2 patients. In 18 of 20 (90%) patients MV annulus size was larger than 95% of predicted normal values. TV abnormalities were found in 12 of 50 (24%) patients with MA. The TV was myxomatous in 4 patients, prolapsing in 2, and redundant in 3, and moderate TV regurgitation was found in 3 patients. In 29 of 50 (58%) patients TV annulus size was larger than 95% of predicted normal values. Contralateral AVV abnormalities in tricuspid and mitral valve atresia are common and should be assessed carefully before surgical procedures.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42381/1/246-20-3-200_20n3p200.pd

An addressable quantum dot qubit with fault-tolerant control fidelity

Exciting progress towards spin-based quantum computing has recently been made with qubits realized using nitrogen-vacancy (N-V) centers in diamond and phosphorus atoms in silicon, including the demonstration of long coherence times made possible by the presence of spin-free isotopes of carbon and silicon. However, despite promising single-atom nanotechnologies, there remain substantial challenges in coupling such qubits and addressing them individually. Conversely, lithographically defined quantum dots have an exchange coupling that can be precisely engineered, but strong coupling to noise has severely limited their dephasing times and control fidelities. Here we combine the best aspects of both spin qubit schemes and demonstrate a gate-addressable quantum dot qubit in isotopically engineered silicon with a control fidelity of 99.6%, obtained via Clifford based randomized benchmarking and consistent with that required for fault-tolerant quantum computing. This qubit has orders of magnitude improved coherence times compared with other quantum dot qubits, with T_2* = 120 mus and T_2 = 28 ms. By gate-voltage tuning of the electron g*-factor, we can Stark shift the electron spin resonance (ESR) frequency by more than 3000 times the 2.4 kHz ESR linewidth, providing a direct path to large-scale arrays of addressable high-fidelity qubits that are compatible with existing manufacturing technologies

The role of input noise in transcriptional regulation

Even under constant external conditions, the expression levels of genes fluctuate. Much emphasis has been placed on the components of this noise that are due to randomness in transcription and translation; here we analyze the role of noise associated with the inputs to transcriptional regulation, the random arrival and binding of transcription factors to their target sites along the genome. This noise sets a fundamental physical limit to the reliability of genetic control, and has clear signatures, but we show that these are easily obscured by experimental limitations and even by conventional methods for plotting the variance vs. mean expression level. We argue that simple, global models of noise dominated by transcription and translation are inconsistent with the embedding of gene expression in a network of regulatory interactions. Analysis of recent experiments on transcriptional control in the early Drosophila embryo shows that these results are quantitatively consistent with the predicted signatures of input noise, and we discuss the experiments needed to test the importance of input noise more generally.Comment: 11 pages, 5 figures minor correction