Preparation and characterization of chitosan‐based dispersions

Complexation of chitosan in aqueous solutions by low molecular weight electrolytes is one of the simplest methods for the preparation of aqueous chitosan dispersions. In this work, the influence of storage time, sulfate concentration, method of preparation and surfactant content on some properties of the resultant chitosan dispersions (turbidity, viscosity and zeta potential) was analyzed. Turbidimetry was adequate to monitor the formation of particles, while viscometry was suitable to monitor changes in the dispersing phase. An analysis of the properties of these systems, mainly in terms of particle–particle and macromolecule–macromolecule interactions was carried out. Copyright © 2004 Society of Chemical Industry     

Scanning laser photostimulation: a new approach for analyzing brain circuits

A new technique for understanding the organization of complex circuits in the vertebrate brain, scanning laser photostimulation, is described. This approach is based on the photolysis of a caged form of the excitatory neurotransmitter glutamate. Computer-controlled photostimulation and whole cell recording in brain slices allow the construction of detailed maps of the position, strength, sign and number of inputs converging on a single postsynaptic neuron. Scanning laser photostimulation offers many advantages over current techniques: spatial resolution is superb, fibers of passage are not activated, and thousands of presynaptic locations can be stimulated. This review describes the technique of photostimulation, outlines the instrumentation, necessary to implement it, and discusses the interpretation of photostimulation-derived data. Several examples of applications, ranging from mapping circuits in the mammalian visual cortex to determining receptor distributions on single neurons are considered. Although still in its early stages, scanning laser photostimulation offers neuroscientists a powerful tool for determining the organization and function of local brain circuits.     

Organization of the genes encoding p-aminobenzoic acid synthetase from Streptomyces lividans 1326

The selective 5HT3 antagonist tropisetron was studied in 91 outpatients meeting DSM-III criteria for Generalized Anxiety Disorder. Following a placebo washout period of up to 1 week, one of three active treatments (tropisetron 0.5 mg, 5 mg, or 25 mg daily) or placebo was given for a further 3 weeks. After 7 days treatment termination rates due to inefficacy showed a statistically significant dose-related therapeutic effect of tropisetron. Similar effects were seen on the Hopkins Symptom Check List total score and the Global Impression Scale. The Hamilton Anxiety Scale showed a similar trend which, however, failed to reach statistical significance. At day 21 tropisetron showed significant dose-dependent effects on all anxiety-related outcome measures. The incidence of adverse events was low and the severity generally mild. Most frequent complaints were headache, nausea, constipation and nervousness. Laboratory tests and physical examination performed at baseline and study end showed no significant treatment effects.     

Can bilharziasis be considered a health priority in western Africa, justifying control programs of large scope?

INTRODUCTION: The aim of the study was the evaluation of the usefulness of transesophageal atrial pacing in predicting chronic oral treatment efficacy of symptomatic reciprocating supraventricular tachycardia in infants and in avoiding the risk of very dangerous recurrences at home. METHODS: We studied 13 infants (11 males, 2 females, mean age 43 +/- 31 days) with symptomatic reciprocating supraventricular tachycardia and no structural heart disease. All patients had chronic oral therapy, using the drug effective in acute i.v. somministration. Each patient was discharged when supraventricular tachycardia was not inducible with transesophageal atrial pacing after 5 half-lives of the drug used in chronic oral treatment. All patients, every 6 months, were retested with transesophageal atrial pacing alternatively during chronic oral therapy and after complete wash out. Oral therapy was stopped in each patient when supraventricular tachycardia was not inducible after the wash out. RESULTS: The number of oral treatments tested for each patient were 2 +/- 1 (range 1-5). The number of transesophageal studies performed for each patient were 4 +/- 2 (range 3-7). No patient had symptomatic episodes of supraventricular tachycardia or needed to change therapy during the follow-up. The oral treatment was stopped after the twelfth month of life in 8 patients and after the twenty-fourth in 2 others without recurrences. CONCLUSION: Transesophageal atrial pacing seems to be useful in predicting accurately and rapidly the oral treatment efficacy of supraventricular tachycardia in infants. Our protocol seems to be effective to avoid dangerous recurrences of tachycardia and to decide when we can stop therapy without risk.     

Allergic rhinoconjunctivitis treated with intramuscular injection of glucocorticoid

Effects and side effects of injectable depot steroid in the treatment of allergic rhinoconjunctivitis (hay fever) are described. A few controlled studies have shown injectable steroids to be superior to the effect of placebo and locally applied steroid. Over a period of 10 years from 1984-95 only 26 registered side effects were reported to the central Danish register for side effects of drugs (Laegemiddelstyrelsens Bivirkningsregister). Only eight concerned subcutaneous atrophy and in two cases the cutaneous changes persisted. Based on registration of number of treatments in the county of Funen 1996, it is estimated that the use of injectable depot steroids for treatment of hay fever accounts for about 535,000 DDD (defined daily doses corresponding to about 33,000 treatments per year). We conclude that the use of injectable corticosteroids in the treatment of hay fever is common and effective and side effects are very rare. However, injectable corticosteroids should only be used when conventional treatment is not sufficient to control symptoms.     

Conformational stability of factor VIIa: biophysical studies of thermal and guanidine hydrochloride-induced denaturation

The binding of the multidomain protein factor VIIa (fVIIa) to tissue factor provides the interprotein communication necessary to make fVIIa an efficient catalyst of the initial event in the extrinsic pathway of blood coagulation. We have investigated the stability of individual domains in fVIIa and the influence of Ca2+ and an irreversible active-site inhibitor (FFR-chloromethyl ketone). Equilibrium guanidine hydrochloride (GuHCl)-induced unfolding monitored by tryptophan fluorescence and far-UV circular dichroism (CD) demonstrated that the gamma-carboxyglutamic acid (Gla) domain unfolds at 0.3 M GuHCl and the serine protease (SP) domain at 3 M GuHCl and that Ca2+ is a prerequisite for the formation of an ordered, compact structure in the Gla domain. The loss of amidolytic activity coincides with the first transition, which is stabilized by the active-site inhibitor, and a change in the environment of the active site is demonstrated using a fluorescent inhibitor (DEGR-chloromethyl ketone). Thermal unfolding monitored by differential scanning calorimetry (DSC) reveals that Ca2+ stabilizes the SP domain slightly, increasing the unfolding temperature by 2.7 degrees C. In addition, Ca2+ is required for a large enthalpy change concomitant with unfolding of the Gla domain, and this unfolding enthalpy is only detectable in the presence of the SP domain, indicating some kind of interaction between these domains. Thermal unfolding measured by CD indicates secondary structural changes at the same temperature as the heat absorption in the DSC but only when both the Gla domain and the SP domain are present together with Ca2+ ions. Taken together, these results indicate a Ca2+-dependent interaction between the Gla domain and the SP domain, implying a high degree of flexibility of the domains in free fVIIa. It is also shown that the epidermal growth factor-like domains are stable at elevated temperatures and high GuHCl concentrations. Moreover, already at physiological temperature, subtle structural changes take place which influence the overall shape of fVIIa and are detrimental to its enzymatic activity.     

Multimedia Stream Binding for a Pan-European Services Platform

The ability to carry stream information over a range of network types in a managed way will become an essential requirement for telecommunications network operators as future services evolve to include the transmission of audio/video and bulk data streams. This paper details the architecture of a working pan-European demonstrator offering multimedia services through the integration of stream control, as specified in the Object Management Group's (OMG's) control and management of audio/video streams, with a TINA-compliant service management environment. This CORBA-based demonstrator, known as the EURESCOM services platform (ESP), has been developed by six European telecommunications companies within EURESCOM project P715. Various modelling concepts, as defined by TINA, ODP and OMG, have been used and verified in a first prototype implementation, with connectivity provided by commercially available multimedia technology such as H.320/323 products. This EURESCOM services platform prototype is one of the first demonstrators world-wide to implement OMG's control and management of audio/video streams specification.     

10 GHz hybrid modelocking of monolithic InGaAs quantum dot lasers

Hybrid modelocking of monolithic quantum dot lasers is reported for the first time. A marked performance improvement over passive modelocking is demonstrated. Both hybrid and passive modelocking at /spl sim/10 GHz are achieved for the first time in quantum dot lasers.