Membrane bound pyrophosphatase and P-type adenosine triphosphatase of Leishmania donovani as possible chemotherapeutic targets: similarities and differences in inhibitor sensitivities

The activities of inorganic pyrophosphatase (PPase) and adenosine triphosphatase (ATPase) were studied in the plasma membrane of Leishmania donovani promastigotes and amastigotes. It was shown that the specific activity of PPase was greater than that of ATPase in the promastigote plasma membrane. We characterized H+-PPase present in the plasma membrane of L. donovani and investigated its possible role in the survival of promastigote and amastigote. PPase activity was stimulated by K+ and sodium orthovanadate and inhibited by pyrophosphate analogs (imidodiphosphate and alendronate), KF, N,N'-dicyclohexylcarbodiimide (DCCD), thiol reagents (p-chloromercuribenzenesulfonate (PCMBS), N-ethylmaleimide (NEM), and phenylarsine oxide (PAO)), the ABC superfamily transport modulator verapamil, and also by the F(1)F(o)-ATPase inhibitor quercetin. ATPase activity was stimulated by K+ and verapamil, inhibited by DCCD, PCMBS, NEM, sodium azide, sodium orthovanadate, and quercetin, and was unaffected by PAO. We conclude that there are significant differences within promastigote, amastigote, and mammalian host in cytosolic pH homeostasis to merit the inclusion of PPase transporter as a putative target for rational drug design.

Stress correlations in granular materials: an entropic formulation

We study the response of dry granular materials to external stress using experiment, simulation, and theory. We derive a Ginzburg-Landau functional that enforces mechanical stability and positivity of contact forces. In this framework, the elastic moduli depend only on the applied stress. A combination of this feature and the positivity constraint leads to stress correlations whose shape and magnitude are extremely sensitive to the nature of the applied stress. The predictions from the theory describe the stress correlations for both simulations and experiments semiquantitatively.

Why do granular materials stiffen with shear rate? Test of novel stress-based statistics

Recent experiments exhibit a rate dependence for granular shear such that the stress grows linearly in the logarithm of the shear rate, gamma. Assuming a generalized activated process mechanism, we show that these observations are consistent with a recent proposal for a stress-based statistical ensemble. By contrast, predictions for rate dependence using conventional energy-based statistical mechanics to describe activated processes, predicts a rate dependence of (ln(gamma))(1/2).

Monitoring dopants by Raman scattering in an electrochemically top-gated graphene transistor

The recent discovery of graphene has led to many advances in two-dimensional physics and devices. The graphene devices fabricated so far have relied on SiO(2) back gating. Electrochemical top gating is widely used for polymer transistors, and has also been successfully applied to carbon nanotubes. Here we demonstrate a top-gated graphene transistor that is able to reach doping levels of up to 5x1013 cm-2, which is much higher than those previously reported. Such high doping levels are possible because the nanometre-thick Debye layer in the solid polymer electrolyte gate provides a much higher gate capacitance than the commonly used SiO(2) back gate, which is usually about 300 nm thick. In situ Raman measurements monitor the doping. The G peak stiffens and sharpens for both electron and hole doping, but the 2D peak shows a different response to holes and electrons. The ratio of the intensities of the G and 2D peaks shows a strong dependence on doping, making it a sensitive parameter to monitor the doping.

Dynamics of an idealized model of microtubule growth and catastrophe

We investigate a simple dynamical model of a microtubule that evolves by attachment of guanosine triphosphate (GTP) tubulin to its end, irreversible conversion of GTP to guanosine diphosphate (GDP) tubulin by hydrolysis, and detachment of GDP at the end of a microtubule. As a function of rates of these processes, the microtubule can grow steadily or its length can fluctuate wildly. In the regime where detachment can be neglected, we find exact expressions for the tubule and GTP cap length distributions, as well as power-law length distributions of GTP and GDP islands. In the opposite limit of instantaneous detachment, we find the time between catastrophes, where the microtubule shrinks to zero length, and determine the size distribution of avalanches (sequence of consecutive GDP detachment events). We obtain the phase diagram for general rates and verify our predictions by numerical simulations.

Impact of zinc supplementation on subsequent morbidity and growth in Bangladeshi children with persistent diarrhoea

This study was conducted to explore whether supplementation of zinc to children during persistent diarrhoea has any subsequent effect on morbidity and growth. A prospective follow-up study was conducted among children, aged 3-24 months, with persistent diarrhoea, who participated earlier in a double-blind randomized placebo-controlled trial. During persistent diarrhoea, children were randomly allocated to receive either zinc in multivitamin syrup or only multivitamin syrup for two weeks. After recovering from diarrhoea, 76 children in the multi-vitamin syrup and 78 children in the zinc plus multivitamin syrup group were followed up for subsequent morbidity and growth. Weekly morbidity and two-weekly anthropometric data were collected for the subsequent 12 weeks. Data showed that episodes and duration of diarrhoea were reduced by 38% and 44% respectively with supplementation of zinc. There was no significant difference in the incidence or duration of respiratory tract infection between the zinc-supplemented and the non-supplemented group. Improved linear growth was observed in underweight children (weight-for-age <70% of the National Center for Health Statistics standard) who received zinc compared to those who did not receive.

Clinical predictors and risk of optic pathway glioma (OPG) in Neurofibromatosis-1 (NF-1)

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Background: NF-1 is a progressive disease with wide spectrum of phenotype and unpredictability in clinical course. NF-1 patients are at significantly increased risk for development of a variety of neoplasms that cause morbidity and limited mortality, including OPG. There are limited data identifying risk factors predictive of subsequent OPG development. Objective: To identify key early clinical features which predict subsequent risk for development of OPG. Methods: Case-control study of NF-1 patients with and without OPG from Cincinnati Children’s Hospital NF-1 and Cancer Registries. Predictor variables were clinical risk factors (age at diagnosis of NF-1, race/ethnicity, gender, and history of familial NF-1, macrocephaly, plexiform neurofibroma, developmental delay, seizure disorder,), and the dependent variable was development of OPG by imaging. Patients received screening head MRI at the time of presentation with NF-1. Odds ratios (O.R.) were calculated with 75 cases (NF-1 and OPG) and 215 controls (NF-1 only) and statistically/clinically significant factors were further analyzed by logistic regression method. Results: Prevalence of OPG in NF-1 was 15.6%. Almost half had familial NF-1. Median age at diagnosis of NF-1 was 1.6 yrs (cases) and 2.4 yrs (controls). OPG was diagnosed at median age 4 yrs. Patients with T2 hyperintense lesions on imaging (UBOs) and age 4 years or less at diagnosis of NF-1 were at significantly increased risk of developing OPG (O.R=3.1, p=0.006 and O.R=3.1, p=0.002 respectively). In addition, presence of seizure disorder and developmental delay were borderline significant (O.R=2.8, p=0.07 and O.R=1.7, p=0.04 respectively). Race (Caucasian) appeared to have disease modifying effect on development and progression of OPG. Conclusions: Patients with T2 lesions on presentation MRI, developmental delay, seizures, and age 4 years or less at NF-1 diagnosis appear to be at an increased risk of developing OPG. Caucasian race appears to have a modifying effect on disease progression. Patients with these risk factors may be stratified as “high risk” and may benefit from close surveillance for early detection of OPG. The association of developmental delay and seizures may suggest a pathophysiologic relationship.

No significant financial relationships to disclose.

Validation of a 7-point Global Overall Symptom scale to measure the severity of dyspepsia symptoms in clinical trials

BACKGROUND

Currently there is no consensus on the optimal method to measure the severity of dyspepsia symptoms in clinical trials.

AIM

To validate the 7-point Global Overall Symptom scale.

METHODS

The Global Overall Symptom scale uses a 7-point Likert scale ranging from 1 = no problem to 7 = a very severe problem. Validation was performed in two randomized-controlled trials (n = 1121 and 512). Construct validity: Global Overall Symptom was compared with the Quality of Life in Reflux And Dyspepsia, Gastrointestinal Symptom Rating Scale, Reflux Disease Questionnaire and 10 specific symptoms using Spearman correlation coefficients. Test-retest reliability: The Intraclass Correlation Coefficient was calculated for patients with stable dyspepsia defined by no change in Overall Treatment Effect score over two visits. Responsiveness: effect size and standardized response mean were also calculated.

RESULTS

Construct validity: Change in Global Overall Symptom score correlated significantly with Quality of Life for Reflux And Dyspepsia, Gastrointestinal Symptom Rating Scale, Reflux Disease Questionnaire and specific symptoms (all P < 0.0002). Reliability: The Intraclass Correlation Coefficient was 0.62 (n = 205) and 0.42 (n = 270). Responsiveness: There was a positive correlation between change in Global Overall Symptom and change in symptom severity. The effect size and standardized response mean were 1.1 and 2.1, respectively.

CONCLUSION

The Global Overall Symptom scale is a simple, valid outcome measure for dyspepsia treatment trials.

Risk factors for mortality due to shigellosis: a case-control study among severely-malnourished children in Bangladesh

To determine the risk factors for death of severely-malnourished Bangladeshi children with shigellosis, a case-control study was conducted at the Clinical Research and Service Centre of ICDDR,B: Centre for Health and Population Research in Dhaka, Bangladesh. One hundred severely-malnourished children (weight-for-age <60% of median of the National Center for Health Statistics), with a positive stool culture for Shigella dysenteriae type 1 or S. flexneri, who died during hospitalization, were compared with another 100 similar children (weight-for-age <60% and with S. dysenteriae type 1 or S. flexneri-associated infection) discharged alive. Children aged less than four years were admitted during December 1993-January 1999. The median age of the cases who died or recovered was 9 months and 12 months respectively. Bronchopneumonia, abdominal distension, absent or sluggish bowel sound, clinical anaemia, altered consciousness, hypothermia, clinical sepsis, low or imperceptible pulse, dehydration, hypoglycaemia, high creatinine, and hyperkalaemia were all significantly more frequent in cases than in controls. In multivariate regression analysis, altered consciousness (odds ratio [OR]=2.6, 95% confidence interval [CI] 1.0-6.8), hypoglycaemia (blood glucose <3 mmol/L (OR=7.8, 95% CI 2.9-19.6), hypothermia (temperature <36 degrees C) (OR=5.7, 95% CI 1.5-22.1), and bronchopneumonia (OR=2.5, 95% CI 1.1-5.5) were identified as significant risk factors for mortality. Severely-malnourished children with shigellosis having hypoglycaemia, hypothermia, altered consciousness and/or bronchopneumonia were at high risk of death. Based on the findings, the study recommends that early diagnosis of shigellosis in severely-malnourished children and assertive therapy for proper management to prevent development of hypothermia, hypoglycaemia, bronchopneumonia, or altered consciousness and its immediate treatment are likely to reduce Shigella-related mortality in severely-malnourished children.

Heartburn-dominant, uninvestigated dyspepsia: a comparison of 'PPI-start' and 'H2-RA-start' management strategies in primary care--the CADET-HR Study

BACKGROUND

There are few data on empiric, stepped therapy for heartburn relief or subsequent relapse in primary care.

AIMS

To compare heartburn relief produced by a proton pump inhibitor-start or an H(2)-receptor antagonist-start with step-up therapy, as needed, followed by a treatment-free period to assess relapse.

METHODS

Heartburn-dominant uninvestigated dyspepsia patients from 46 primary care centres were randomized to one of two active treatment strategies: omeprazole 20 mg daily (proton pump inhibitor-start) or ranitidine 150 mg bid (H2-receptor antagonist-start) for the first 4-8 weeks, stepping up to omeprazole 40 or 20 mg daily, respectively, for 4-8 weeks for persistent symptoms. Daily diaries documented heartburn relief (score < or = 3/7 on < or = of 7 prior days) and relapse (score > or = 4 on > or = 2 of 7 prior days).

RESULTS

For 'proton pump inhibitor-start' (n = 196) vs. 'H2-receptor antagonist-start' (n = 194), respectively, heartburn relief occurred in 55.1% vs. 27.3% (P < 0.001) at 4 weeks and in 88.3% vs. 87.1% at 16 weeks. After therapy, 308 patients were heartburn-free (159 vs. 149); median times to relapse were 8 vs. 9 days and cumulative relapse rates were 78.6% vs. 75.8%, respectively.

CONCLUSIONS

An empiric 'proton pump inhibitor-start' strategy relieves heartburn more effectively than an 'H2-receptor antagonist-start' strategy up to 12 weeks but has no effect on subsequent relapse, which is rapid in most patients.

The prevalence of clinically significant endoscopic findings in primary care patients with uninvestigated dyspepsia: the Canadian Adult Dyspepsia Empiric Treatment - Prompt Endoscopy (CADET-PE) study

BACKGROUND

Uninvestigated dyspepsia is common in family practice. The prevalence of clinically significant upper gastrointestinal findings (CSFs) in adult uninvestigated dyspepsia patients, and their predictability based on history, is unknown.

METHODS

Prompt endoscopy was performed within 10 days of referral, in 1040 adult patients presenting with uninvestigated dyspepsia at 49 Canadian family practitioner centres. Subsequent management strategies during a 6-month follow-up period were determined by the individual family practitioners.

RESULTS

CSFs were identified in 58% (603/1040) of patients. Erosive oesophagitis was most common (43%; N = 451); peptic ulcer was uncommon (5.3%; N = 55). Alarm symptoms were uncommon (2.8%; N = 29). Most patients had at least three dyspepsia symptoms, more than 80% had at least six, and approximately half had eight or more. Based on the dominant symptom, 463 (45%) patients had ulcer-like, 393 (38%) had reflux-like and 184 (18%) had dysmotility-like dyspepsia. The patients' dominant symptom was not predictive of endoscopic findings. Oesophagitis was more common in those with dominant reflux-like symptoms and was the most common finding in all subgroups. The prevalence of gastroduodenal findings was similar in all symptom subgroups. Helicobacter pylori (H. pylori) infection (30%; 301/1013) was associated with gastroduodenal findings.

CONCLUSIONS

Dyspepsia subclassifications, based on dominant symptom, are of limited value in predicting the presence and nature of CSFs. Oesophagitis was by far the most common diagnosis (43% of patients). CSFs were common in uninvestigated dyspepsia patients and their nature suggests patients could be initially treated effectively, without endoscopy, using empirical acid suppressive therapy.

Topological jamming and the glass transition in a frustrated system

The relationship between extended structures, glassy dynamics and an underlying critical point is examined in the context of a lattice model of fluctuating lines. Monte Carlo simulations are used to construct an effective, coarse-grained dynamics for the "order parameter" near the critical point. Analysis of the effective dynamics reveals that the critical point is associated with diverging barriers leading to the observed Vogel-Fulcher divergence of the relaxation times. A direct connection is established between the presence of extended structures and the activated dynamics.

Electron microscopic studies of the corpuscles of Stannius of an airbreathing teleost (Heteropneustes fossilis)

The ultrastructure of the corpuscles of Stannius (CS) of Heteropneustes fossilis reveals a homogenous cellular composition characterized by only one cell type, with large secretory granules and abundant ribosomal endoplasmic reticulum. These cells are comparable to the type 1 cell described in the CS of other teleosts; type 2 cells, whose presence is ubiquitous in the CS of freshwater species are absent in H. fossilis. Our data on the CS of H. fossilis demonstrate that not all freshwater species possess type 2 cells in their CS and these are not essential for life in freshwater

Entropy-vanishing transition and glassy dynamics in frustrated spins

In an effort to understand the glass transition, the dynamics of a nonrandomly frustrated spin model has been analyzed. The phenomenology of the spin model is similar to that of a supercooled liquid undergoing the glass transition. The slow dynamics can be associated with the presence of extended stringlike structures which demarcate regions of fast spin flips. An entropy-vanishing transition, with the string density as the order parameter, is related to the observed glass transition in the spin model.

Charge-transfer complex formation between o-chloranil and a series of polynuclear aromatic hydrocarbons

The equilibrium constants, enthalpies and entropies of formation of molecular electron donor-acceptor (EDA) complexes of o-chloranil with a series of aromatic hydrocarbons have been determined spectrophotometrically. Spectroscopic and thermodynamic aspects of these complexes have been analysed.

Kinetics of ordering in fluctuation-driven first-order transitions: simulation and theory

Many systems involving competing interactions or interactions that compete with constraints are well described by a model first introduced by Brazovskii [Zh. Eksp. Teor. Fiz. 68, 175 (1975) [Sov. Phys. JETP 41, 85 (1975)]]. The hallmark of this model is that the fluctuation spectrum is isotropic and has a maximum at a nonzero wave vector represented by the surface of a d-dimensional hypersphere. It was shown by Brazovskii that the fluctuations change the free energy structure from a straight phi(4) to a straight phi(6) form with the disordered state metastable for all quench depths. The transition from the disordered phase to the periodic lamellar structure changes from second order to first order and suggests that the dynamics is governed by nucleation. Using numerical simulations we have confirmed that the equilibrium free energy function is indeed of a straight phi(6) form. A study of the dynamics, however, shows that, following a deep quench, the dynamics is described by unstable growth rather than nucleation. A dynamical calculation, based on a generalization of the Brazovskii calculations, shows that the disordered state can remain unstable for a long time following the quench.