Neuroimaging findings in adolescent gaming disorder: a systematic review.

OBJECTIVES: Gaming disorder is a growing concern affecting adolescents, exacerbated by the impact of recent COVID-19 restrictions. The World Health Organization has recently included gaming disorder in the 11th International Classification of Diseases (ICD-11). However, there is still an ongoing debate about the validity and reliability of the proposed clinical criteria, despite growing neurobiological evidence in this cohort. Systematic reviews in this area have focused mainly on adults or mixed adult/adolescent populations. Therefore, this systematic review explored the neuroimaging literature in adolescents (under 18 years old) with gaming disorder. METHODS: Using PRISMA 2020 guidelines, 3288 primary studies were identified from PubMed, CINAHL Plus, PsycINFO and Web of Science. After applying inclusion and exclusion criteria (appropriate title, abstract, comparison group used within study, English-language, neuroimaging and mean age under 18), 24 studies were included in this review. RESULTS: Functional and structural brain alterations in adolescent gaming disorder were noted across several imaging modalities, including electroencephalogram (EEG), functional magnetic resonance imaging (fMRI) and structural magnetic resonance imaging (MRI). Compared with healthy controls, adolescents with gaming disorder demonstrated neurological changes comparable to substance addiction, namely impairments in emotional regulation, reward-seeking, inhibition and increased risky decision-making. Positive brain adaptations in the areas of visuospatial processing and memory were observed. CONCLUSIONS: A number of key brain regions are affected in adolescent gaming disorder. These findings can help clinicians understand adolescent presentations with gaming disorder from a neurobiological perspective. Future studies should focus on forming a robust neurobiological and clinical framework for adolescent gaming disorder.

Obesity Definitions in Sarcopenic Obesity: Differences in Prevalence, Agreement and Association with Muscle Function.

BACKGROUND: Sarcopenic obesity (SO) is associated with poorer physical performance in the elderly and will increase in relevance with population ageing and the obesity epidemic. The lack of a consensus definition for SO has resulted in variability in its reported prevalence, poor inter-definitional agreement, and disagreement on its impact on physical performance, impeding further development in the field. While sarcopenia definitions have been compared, the impact of obesity definitions in SO has been less well-studied. OBJECTIVES: To compare 3 widely-adopted definitions of obesity in terms of SO prevalence, inter-definitional agreement, and association with muscle function. DESIGN: Cross-sectional. SETTING: GERILABS study, Singapore Participants: 200 community-dwelling, functionally-independent older adults. MEASUREMENTS: We utilized three commonly-used definitions of obesity: body mass index (BMI), waist circumference (WC) and DXA-derived fat mass percentage (FM%). Sarcopenia was defined using Asian Working Group for Sarcopenia criteria. For muscle function, we assessed handgrip strength, gait speed and Short Physical Performance Battery (SPPB). Subjects were classified into 4 body composition phenotypes (normal, obese, sarcopenic and SO), and outcomes were compared between groups. RESULTS: The prevalence rate for SO was lowest for BMI (0.5%) compared to FM% (10.0%) and WC (10.5%). Inter-definitional agreement was lowest between BMI and WC (κ=0.364), and at best moderate between FM% and WC (κ=0.583). SO performed the worst amongst body composition phenotypes in handgrip strength, gait speed and SPPB (all p<0.01) only when defined using WC. In regression analyses, SO was associated with decreased SPPB scores (ß=-0.261, p=0.001) only for the WC definition. CONCLUSION: There is large variation in the prevalence of SO across different obesity definitions, with low-to-moderate agreement between them. Our results corroborate recent evidence that WC, and thus central obesity, is best associated with poorer muscle function in SO. Thus, WC should be further explored in defining obesity for accurate and early characterization of SO among older adults in Asian populations.

Characterization of chitosan acetate as a binder for sustained release tablets.

A chitosan derivative as an acetate salt was successfully prepared by using a spray drying technique. Physicochemical characteristics and micromeritic properties of spray-dried chitosan acetate (SD-CSA) were studied as well as drug-polymer and excipient-polymer interaction. SD-CSA was spherical agglomerates with rough surface and less than 75 microm in diameter. The salt was an amorphous solid with slight to moderate hygroscopicity. The results of Fourier transform infrared (FTIR) and solid-state (13)C NMR spectroscopy demonstrated the functional groups of an acetate salt in its molecular structure. DSC and TGA thermograms of SD-CSA as well as FTIR and NMR spectrum of the salt, heated at 120 degrees C for 12 h, revealed the evidence of the conversion of chitosan acetate molecular structure to N-acetylglucosamine at higher temperature. No interaction of SD-CSA with either drugs (salicylic acid and theophylline) or selected pharmaceutical excipients were observed in the study using DSC method. As a wet granulation binder, SD-CSA gave theophylline granules with good flowability (according to the value of angle of repose, Carr's index, and Hausner ratio) and an excellent compressibility profile comparable to a pharmaceutical binder, PVP K30. In vitro release study of theophylline from the tablets containing 3% w/w SD-CSA as a binder demonstrated sustained drug release in all media. Cumulative drug released in 0.1 N HCl, pH 6.8 phosphate buffer and distilled water was nearly 100% within 6, 16 and 24 h, respectively. It was suggested that the simple incorporation of spray-dried chitosan acetate as a tablet binder could give rise to controlled drug delivery systems exhibiting sustained drug release.

Automating the drug scheduling of cancer chemotherapy via evolutionary computation.

This paper presents the optimal control of drug scheduling in cancer chemotherapy using a distributed evolutionary computing software. Unlike conventional methods that often require gradient information or hybridization of different approaches in drug scheduling, the proposed evolutionary optimization methodology is simple and capable of automatically finding the near-optimal solutions for complex cancer chemotherapy problems. It is shown that different number of variable pairs in evolutionary representation for drug scheduling can be easily implemented via the software, since the computational workload is shared and distributed among multiple computers over the Internet. Simulation results show that the proposed evolutionary approach produces excellent control of drug scheduling in cancer chemotherapy, which are competitive or equivalent to the best solutions published in literature.

Chitosan-alginate-CaCl(2) system for membrane coat application.

Water-based formulations are preferred for membrane coat application because they do not require the use of noxious solvents. A novel aqueous chitosan-alginate-CaCl(2) system was evaluated as a potential formulation to produce water-insoluble membranes of biodegradable polymers. Chitosan-alginate coacervates were prepared by controlled reaction of chitosan (0.25% w/v) and sodium alginate (0.25% w/v) solutions. Coherent membranes were obtained by casting and drying the coacervates suspended in aqueous CaCl(2) solutions (0.05-0.07% w/v). Increasing the calcium content did not modify membrane thickness (25-26 microm), but reduced the water vapor transmission rate from 658 to 566 g/m(2)/day, and improved the tensile strength of the membranes from 9.33 to 17.13 MPa. Differential scanning calorimetry, Fourier transform infrared spectroscopy, and elemental analyses of the chitosan-alginate coacervates indicated they were stable for up to 4 weeks of storage in distilled water at ambient temperature. Membranes of the stored coacervates required less calcium to attain maximum mechanical strength. They also had higher water vapor transmission rates than corresponding films prepared from fresh coacervates. On the basis of the properties of the cast film and its storage stability, the chitosan-alginate-CaCl(2) system can be considered for potential membrane coat application.

Chitosan-alginate films prepared with chitosans of different molecular weights.

Chitosan-alginate polyelectrolyte complex (CS-AL PEC) is water insoluble and more effective in limiting the release of encapsulated materials compared to chitosan or alginate. Coherent CS-AL PEC films have been prepared in our laboratory by casting and drying suspensions of chitosan-alginate coacervates. The objective of this study was to evaluate the properties of the CS-AL PEC films prepared with chitosans of different molecular weights. Films prepared with low-molecular-weight chitosan (Mv 1.30 x 10(5)) were twice as thin and transparent, as well as 55% less permeable to water vapor, compared to films prepared with high-molecular-weight chitosan (Mv 10.0 x 10(5)). It may be inferred that the low-molecular-weight chitosan reacted more completely with the sodium alginate (M(v) 1.04 x 10(5)) than chitosan of higher molecular weight. A threshold molecular weight may be required, because chitosans of Mv 10.0 x 10(5) and 5.33 x 10(5) yielded films with similar physical properties. The PEC films exhibited different surface properties from the parent films, and contained a higher degree of chain alignment with the possible formation of new crystal types. The PEC films exhibited good in vitro biocompatibility with mouse and human fibroblasts, suggesting that they can be further explored for biomedical applications.

Concurrent production of chitin from shrimp shells and fungi.

Crustacean shells constitute the traditional and current commercial source of chitin. Conversely, the control of fungal fermentation processes to produce quality chitin makes fungal mycelia an attractive alternative source. Therefore, the exploitation of both of these sources to produce chitin in a concurrent process should be advantageous and is reported here. Three proteolytic Aspergillus niger (strains 0576, 0307 and 0474) were selected from a screening for protease activity from among 34 zygomycete and deuteromycete strains. When fungi and shrimp shell powder were combined in a single reactor, the release of protease by the fungi facilitated the deproteinization of shrimp-shell powder and the release of hydrolyzed proteins. The hydrolyzed proteins in turn were utilized as a nitrogen source for fungal growth, leading to a lowering of the pH of the fermentation medium, thereby further enhancing the demineralization of the shrimp-shell powder. The shrimp-shell powders and fungal mycelia were separated after fermentation and extracted for chitin with 5% LiCl/DMAc solvent. Chitin isolates from the shells were found to have a protein content of less than 5%, while chitin isolates from the three fungal mycelia strains had protein content in the range of 10-15%. The relative molecular weights as estimated by GPC for all chitin samples were in the 10(5) dalton range. All samples displayed characteristic profiles for chitin in their FTIR and solid-state NMR spectra. All chitin samples evaluated with MTT and Neutral Red assays with three commercial cell lines did not display cytotoxic effects.

Preparation and characterization of chitin beads as a wound dressing precursor.

Chitin was dissolved in N, N-dimethylacetamide/5% lithium chloride (DMAc/5%LiCl) to form a 0.5% chitin solution. Chitin beads were formed by dropping the 0.5% chitin solution into a nonsolvent coagulant, ethanol. The beads were left in ethanol for 24 h to permit hardening, consolidation, and removal of residual DMAc/5%LiCl solvent in order to give spherical chitin beads uniform size distribution. The ethanol-gelled chitin beads had an average diameter of 535 microm. The chitin beads were subsequently activated in 50% (w/v) NaOH solution and reacted with 1.9 M monochloroacetic acid/2-propanol solution to introduce a carboxymethylated surface layer to the chitin beads. The bilayer character of the surface-carboxymethylated chitin (SCM-chitin) beads was verified by Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), and confocal microscopy. The bilayered SCM-chitin beads were found to absorb up to 95 times their dry weight of water. These SCM-chitin beads have potential as a component of wound dressings.

A multiobjective evolutionary algorithm toolbox for computer-aided multiobjective optimization.

This paper presents an interactive graphical user interface (GUI) based multiobjective evolutionary algorithm (MOEA) toolbox for effective computer-aided multiobjective (MO) optimization. Without the need of aggregating multiple criteria into a compromise function, it incorporates the concept of Pareto's optimality to evolve a family of nondominated solutions distributing along the tradeoffs uniformly. The toolbox is also designed with many useful features such as the goal and priority settings to provide better support for decision-making in MO optimization, dynamic population size that is computed adaptively according to the online discovered Pareto-front, soft/hard goal settings for constraint handlings, multiple goals specification for logical "AND"/"OR" operation, adaptive niching scheme for uniform population distribution, and a useful convergence representation for MO optimization. The MOEA toolbox is freely available for download at http://vlab.ee.nus.edu.sg/-kctan/moea.htm which is ready for immediate use with minimal knowledge needed in evolutionary computing. To use the toolbox, the user merely needs to provide a simple "model" file that specifies the objective function corresponding to his/her particular optimization problem. Other aspects like decision variable settings, optimization process monitoring and graphical results analysis can be performed easily through the embedded GUIs in the toolbox. The effectiveness and applications of the toolbox are illustrated via the design optimization problem of a practical ill-conditioned distillation system. Performance of the algorithm in MOEA toolbox is also compared with other well-known evolutionary MO optimization methods upon a benchmark problem.

Pattern of sensitization to common environmental allergens amongst atopic Singapore children in the first 3 years of life.

This study was aimed to investigate the sensitization pattern to a range of common allergens in young Singaporean children. A cross-sectional study involving 75 children aged below 3 years was carried out. They presented between December 1995 and April 2000 with symptoms of asthma, rhinitis, eczema, or food allergy. Their levels of allergen-specific serum IgE to a panel of foods (egg white, milk, soy protein, shrimp, wheat and peanut), pet dander, dust mites and cockroaches were measured with Pharmacia CAP System radioallergosorbent test kits. Serum IgE levels greater than 0.35 kU/l represented a positive result. Four children could not be tested with the complete panel because of insufficient serum. The prevalence of sensitization was highest for cow's milk (45.9%) followed by egg white (38.7%), dust mites Dermatophagoides pteronyssinus (31.4%) and Blomia tropicalis (25.5%). Sensitization to ingested allergens was significantly more prevalent in children aged 1 year or younger than in the older children (70.4% of those below 1 year, and 50% of those aged 1-3 years; p < 0.02). Sensitization to inhaled allergens, such as dust mites, was more likely to manifest as respiratory symptoms (allergic rhinitis and asthma), while ingested allergens were associated with gastrointestinal symptoms and eczema (p < 0.001). It was concluded that infants and young children are at high risk of sensitization to common environmental substances. Allergen avoidance is therefore important even in the very young. The prevalence of sensitization to food allergens is higher compared to inhalant allergens in young children.

PEC films prepared from Chitosan-Alginate coacervates.

Chitosan-alginate polyelectrolyte complex (PEC) have been prepared in situ in beads and microspheres. This study examines the preparation of suitable chitosan-alginate coacervates for casting into homogeneous PEC films for potential applications in packaging, controlled release systems and wound dressings. Coacervation between chitosan and alginate was rapid, but the rate may be controlled with the addition of water miscible organic solvents. Compared with ethanol and PEG200, acetone was the more promising solvent moderator. Suspensions of fine, uniformly dispersed coacervates were produced by a dropwise addition of 0.25% w/v chitosan solution (solvent: 1: 1 v/v of 2% acetic acid and acetone) into 0.25% w/v sodium alginate solution in water under rapid agitation. The PEC films were transparent and flexible. They exhibited high permeability to water vapor, but resisted complete dissolution in 0.1 M HCI, distilled water and pH 7.4 phosphate buffer solution. Microscopic heterogeneity in the films could be reduced by immersion in aqueous media, but this was accompanied by modifications in the thickness, permeability and mechanical property of the films.

Invasive Haemophilus influenzae type b infections in Singapore children: a hospital-based study.

OBJECTIVE: A 6-year (1990-95) hospital-based retrospective study was carried out to investigate the pattern of invasive Haemophilus influenzae type b (Hib) disease. METHODOLOGY: Cases with Hib isolated from sterile sites (blood, cerebrospinal fluid, or joint aspirate) were identified from the hospital's microbiological records, and their reviewed case records. Patients with pyogenic meningitis in the same study period were also identified to estimate the incidence of Hib meningitis. RESULTS: Twelve patients had positive cultures from sterile sites, of whom nine children were less than 5 years of age. These included seven cases of meningitis, one patient with acute epiglottitis, and one case of pneumonia. Three of the seven patients with meningitis had significant long-term sequelae. Our data also suggests a relatively low proportion of ethnic Chinese children with invasive disease. It was estimated that 18.4% to 41.1% of pyogenic meningitis in children admitted to the National University Hospital were due to Hib. The estimated annual attack rate of invasive Hib disease was at most 3.3 per 100 000 children aged less than 5 years (95% confidence interval: 2.6-3.5/100 000). CONCLUSION: : Invasive Hib infections are relatively uncommon in our community. This justifies the need for a cost effectiveness study before a universal Hib vaccination program is implemented.

Wound dressing with sustained anti-microbial capability.

To overcome current limitations in wound dressings for treating mustard-burn induced septic wound injuries, a nonadherent wound dressing with sustained anti-microbial capability has been developed. The wound dressing consists of two layers: the upper layer is a carboxymethyl-chitin hydrogel material, while the lower layer is an anti-microbial impregnated biomaterial. The hydrogel layer acts as a mechanical and microbial barrier, and is capable of absorbing wound exudate. In physiological fluid, the carboxymethylated-chitin hydrogel swells considerably, imbibing up to 4 times its own weight of water and is also highly porous to water vapor. The moisture permeability of the dressing prevents the accumulation of fluid in heavily exudating wounds seen in second-degree burns. The lower layer, fabricated from chitosan acetate foam, is impregnated with chlorhexidine gluconate. From the in vitro release studies, the loading concentration was optimized to deliver sufficient anti-microbial drug into the wound area to sustain the anti-microbial activity for 24 h. The anti-microbial activity of the dressing against Pseudomonas aeruginosa and Staphylococcus aureus was tested using the Bauer-Kirby Disk Diffusion Test.

Novel fabrication of open-pore chitin matrixes.

A novel method has been developed to produce open-pore chitin matrixes. Chitin solutions were loaded with calcium carbonate (CaCO3) crystals and the mixture cast to form gels. The CaCO3-chitin gels were submerged in 1 N HCl solution to produce highly porous matrixes with good water vapor permeability, water uptake profile, and enhanced mechanical properties. The open-pore system is obtainable because CaCO3 loaded into the chitin gel reacts with 1 N HCl solution to produce gaseous carbon dioxide. Evolution of carbon dioxide during the reaction results in continuous pore structures from the matrix' bulk to surface. When the concentration of CaCO3 loaded into the chitin gel is controlled, defined homogeneous pores measuring 100-500 and 500-1000 microns, with porosities of approximately 76% and 81%, respectively, can be produced.

Storage of partially deacetylated chitosan films.

Chitosan has wide-ranging applications as a biomaterial, but its stability in storage is not widely known. The objective of this study was to evaluate the storage stability of films prepared from chitosan of 77% deacetylation. Both the neutralized and acetate films were evaluated, as chitosan salts offer the advantage of being soluble in water at the neutral-to-basic pH range. Aqueous solutions containing 0.5-5% acetic acid were used as solvents. The X-ray diffraction pattern, the IR spectrum, water uptake, and solubility of the films were influenced by the presence of the N-acetyl functionality, the acetate ions, and storage of the films. The anhydrous chitosan crystal in the neutralized films was unstable to storage at 4 degrees C and 28 degrees C. Its formation, as well as that of the hydrated crystal, were further hindered by the presence of even small quantities of the acetate ions. The resultant amorphous nature of the acetate films, coupled with the acidifying action of the acetic acid, led to greater water uptake and solubility compared to the neutralized films. Storage reduced the differences between the neutralized and acetate films. It also minimized the influence of the initial acetic acid content on the IR absorption and water uptake of the acetate films, exerting its leveling effects mainly within the first week of storage. Using a lower storage temperature of 4 degrees C or heating the films for 2 h at 120 degrees C prior to storage did not significantly modify the results. A pertinent factor appears to be the degree of deacetylation of the chitosan that was used to prepare the films.

Effects of dry heat and saturated steam on the physical properties of chitosan.

Heat may be employed to facilitate the processing of chitosan and to confer sterility on chitosan-based medical products. In this study, changes were analyzed of the physical properties of purified chitosan heated at 60 to 160 degrees C under specified conditions for periods ranging from 0.5 to 4 h. Two forms of heat were used for processing: dry heat generated by a convection oven and saturated steam generated by an autoclave. Dry heat at < or = 80 degrees C resulted in less rigid chains with lower glass transition temperature, improved aqueous solubility, and slightly higher [eta]. At higher temperatures, dry heat produced chromophores, which may be related to interchain crosslink formation involving the NH2 groups. The [eta] and aqueous solubility of the samples decreased with temperatures > or = 120 degrees C. The coloration of the samples intensified from yellow to brown with increasing temperatures and duration of heat exposure. Chitosan heated at 160 degrees C for > or = 2 h was insoluble in the 0.2 M acetic acid/0.1 M sodium acetate solvent. The rate and extent of the thermal reactions were increased in the presence of saturated steam; the autoclaved samples became insoluble after 2 h of heating at 115 degrees C and after 1 h at > or = 120 degrees C. On the other hand, the physical changes induced by dry heat at < or = 120 degrees C were not affected significantly by heating the chitosan samples under anoxic conditions.

Fluoride release and antibacterial properties of new-generation tooth-colored restoratives.

The aim of this study was to compare the amounts and pattern of fluoride release and antibacterial properties of new-generation restoratives over a 35-day period. Materials evaluated included fluoride-releasing composites (Tetric, Experimental X), compomers (Dyract, Compoglass), and a resin-modified glass-ionomer cement (Fuji II LC). A conventional glass ionomer (Fuji II Cap) was used as a control for fluoride-release testing. Five samples of each restorative material were evaluated for daily fluoride release over a 35-day period by means of ion chromatography. Ranking of materials from least to greatest total fluoride release over 35 days was as follows: Tetric < Experimental X < Dyract < Fuji II LC < Compoglass < Fuji II Cap. Fuji II Cap had significantly greater fluoride release than all other materials evaluated. Fuji II Cap, Fuji II LC, and Compoglass had similar patterns of fluoride release characterized by a high initial release that was many times that released later. The fluoride-releasing composites evaluated stopped releasing fluoride by day 14. Antibacterial testing was conducted using the agar diffusion inhibitory test. Five samples of each restorative were assessed at baseline and weekly intervals up to 35 days. The microorganisms used were Lactobacillus casei, Streptococcus mutans, and Streptococcus sobrinus. IRM, a zinc oxide/eugenol cement, was used as the baseline control. None of the restorative materials evaluated affected the growth of L casei, S sobrinus, or S mutans at all time periods including baseline, where fluoride was detected in the agar beneath the specimen disks. There was no correlation noted between fluoride-release potential and antibacterial properties.

Gamma irradiation of chitosan.

Chitosan has potential biomedical applications that may require the final products to be sterilized before use. The gamma irradiation of purified and highly deacetylated chitosan fibers and films at sterilizing doses (up to 25 kGy) caused main chain scissions. The viscosity average molecular weight of the polymer decreased with increasing irradiation dose, the radiation yields of scission being 1.16 in air and 1.53 in anoxia. Preirradiation application of a negative pressure of 100 kPa disrupted the network structure, which may have contributed to the greater radiation yield obtained by chitosan fibers in anoxia. Radiation induced scission of the chitosan chains resulted in a lower glass transition temperature (Tg), indicative of higher segmental mobility. The Tg was below ambient at an irradiation dose of 25 kGy in air. Irradiation in air improved the tensile strength of the chitosan film, probably due to changes in chain interaction and rearrangement. Irradiation in anoxia did not affect film properties significantly, partly because the preirradiation application of negative pressure had a negligible effect on the structure of the chitosan film. Polymer network structure and the irradiation conditions are therefore important determinants of the extent of radiation induced reactions in chitosan.

Preparation of a chitin-apatite composite by in situ precipitation onto porous chitin scaffolds.

Composites of chitin with calcium phosphate were obtained by in situ precipitation of the mineral from a supersaturated solution onto chitin scaffolds. The chitin scaffolds were obtained by freeze drying to give a highly porous structure possessing a polar surface favorable for apatite nucleation and growth. THe extent and arrangement of calcium phosphate deposits on the chitin and substituted chitin scaffolds were explored. Up to 55% by mass of calcium phosphate could be incorporated into chitin scaffolds. Deposits on the chitin surface were a continuous apatite carpet nature while deposits on carboxymethylated chitin surfaces displayed a spherical morphology. Carboxymethylation of chitin exerts an overall inhibitory effect towards calcium phosphate deposition, but it provides for site-specific nucleation of the mineral phase. In situ precipitation can be an important route in the future production of various polymer-calcium phosphate composites.