Synergistic Interaction of Hyperbranched Polyglycerols and Cetyltrimethylammonium Bromide for Oil/Water Interfacial Tension Reduction: A Molecular Dynamics Study.

Applying surfactants to reduce the interfacial tension (IFT) on water/oil interfaces is a proven technique. The search for new surfactants and delivery strategies is an ongoing research area with applications in many fields such as drug delivery through nanoemulsions and enhanced oil recovery. Experimentally, the combination of hyperbranched polyglycerol (HPG) with cetyltrimethylammonium bromide (CTAB) substantially reduced the observed IFT of oil/water interface, 0.9 mN/m, while HPG alone was 5.80 mN/m and CTAB alone IFT was 8.08 mN/m. Previous simulations in an aqueous solution showed that HPG is a surfactant carrier. Complementarily, in this work, we performed classical molecular dynamics simulations on combinations of CTAB and HPG with one aliphatic chain to investigate further the interaction of this pair in oil interfaces and propose the mechanism of IFT decrease. Basically, from our results, one can observe that the IFT reduction comes from a combination of effects that have not been observed for other dual systems: (i) Due to the CTAB-HPG strong interaction, a weakening of their specific and isolated interactions with the water and oil phases occurs. (ii) Aggregates enlarge the interfacial area, turning it into a less ordered interface. (iii) The spread of individual molecules charge profiles leads to the much lower interfacial tension observed with the CTAB+HPG systems.

[Pulmonary blood flow distribution in acute viral bronchiolitis]. / Distribuição do fluxo sangüíneo pulmonar na bronquiolite viral aguda.

OBJECTIVE: To assess lung perfusion patterns in inpatients with acute viral bronchiolitis using quantitative 99mTc-MAA scintigraphy so as to establish an association with clinical and radiological findings. METHODS: A comparative, prospective case series study with a focus on diagnosis was carried out in a population of patients with acute viral bronchiolitis admitted to Hospital de Clínicas de Porto Alegre. Inclusion criteria were age between 1 and 24 months and first sudden-onset wheezing episode, suggesting bronchiolitis. The patients in the study were submitted to clinical, radiological and 99mTc-MAA lung perfusion evaluation during the first 24 hours of admission. Statistical analysis employed t test, taking into consideration a significance level of 0.05. RESULTS: The regional distribution of lung blood flow in the 38 patients studied was more pronounced in the upper section of the left lung in relation to the right lung (P<0.001). The distribution gradients of blood flow between the upper and middle and upper and lower sections were higher in the left lung (P<0.001). The distribution gradients of blood flow between the middle and lower sections were higher in the right lung, but without significance. The distribution gradient of the pulmonary flow in the anteroposterior axis was >1.0 in the upper and middle sections of both lungs. In the lower section it was >1.0 only in the right lung (P<0.007). There was no association between lung blood flow distribution patterns and clinical or radiological findings. CONCLUSION: There was no evidence of an association between lung blood flow distribution and ventilation-perfusion ratio in hospitalized infants with acute viral bronchiolitis; only a tendency to redirect lung blood flow towards upper lung sections was observed.

Dopamine transporter gene, response to methylphenidate and cerebral blood flow in attention-deficit/hyperactivity disorder: a pilot study.

The homozygosity of the 10-repeat allele at dopamine transporter gene (DAT1) seems to be associated with a poor response to methylphenidate (MPH) in children with attention-deficit/hyperactivity disorder (ADHD). This pilot study aimed to simultaneously assess polymorphisms at DAT1, response to MPH, and neuroimaging. Only ADHD children with at least a moderate response to MPH were included. Significantly higher regional cerebral blood flows assessed by single photon emission computerized tomography (SPECT) were detected in medial frontal and left basal ganglia areas in children with homozygosity for the 10-repeat allele at DAT1 gene (n = 4) than in children without this genotype (n = 4) (P < 0.05). These findings provide a preliminary connection between pharmacogenetics and neurobiological investigations on stimulant treatment of ADHD.

The acute effect of methylphenidate on cerebral blood flow in boys with attention-deficit/hyperactivity disorder.

Methylphenidate (MPH) is the most commonly prescribed treatment for attention-deficit/hyperactivity disorder (ADHD). The therapeutic mechanisms of MPH are not, however, fully understood. We studied the effects of MPH on brain activity in male children and adolescents with ADHD, using the blood flow radiotracer technetium-99m ethyl cysteinate dimer ((99m)Tc-ECD) and single-photon emission tomography (SPET). The study was randomized, double blind, and placebo controlled (MPH group, n=19; placebo group, n=17), Radiotracer was administered during the performance of the Continuous Performance Test and before and after 4 days of MPH treatment. Statistical parametric mapping (SPM99) analysis showed a significant reduction in regional cerebral blood flow in the left parietal region in the MPH group compared with the placebo group (P<0.05, corrected for multiple comparisons). Our findings suggest that the posterior attentional system, which includes the parietal cortex, may have a role in the mediation of the therapeutic effects of MPH in ADHD.

Distribuição do fluxo sangüíneo pulmonar na bronquiolite viral aguda / Pulmonary blood flow distribution in acute viral bronchiolitis

Objetivo: avaliar a distribuiçäo da perfusäo pulmonar em pacientes hospitalizados com bronquiolite aguda, por meio de cintilografia pulmonar perfusional quantitativa com 99mTc-MAA, estabelecendo associaçäo com avaliaçöes clínica e radiológica concomitantes. Pacientes e métodos: foi realizado um estudo de série de casos, prospectivo, comparativo, com enfoque diagnóstico, em amostra por conveniência de pacientes hospitalizados com bronquiolite aguda, baseada em critérios clínicos, idade entre 1 e 12 meses, como primeiro episódio de sibilância expiratória de início súbito, sugestivo de bronquiolite. Foram realizadas avaliaçöes clínica, radiológica e da perfusäo pulmonar nas primeiras 24 horas da admissäo. Foi utilizado o teste t de Student, com o nível de significância de 0,05, na análise estatística.Resultados: nos 38 pacientes estudados, a distribuiçäo do fluxo sangüíneo pulmonar regional foi maior na regiäo superior do pulmäo esquerdo em relaçäo ao direito (p<0,001). Os gradientes de distribuiçäo do fluxo pulmonar entre as regiöes superior e média e superior e inferior foi maior no pulmäo esquerdo (P<0,001), e entre as regiöes média e inferior, foi maior no direito. O gradiente de distribuiçäo do fluxo pulmonar no eixo ântero-posterior foi >1,0 em ambos os pulmöes nas regiöes superior e média; na regiäo inferior, foi >1,0 apenas no pulmäo direito (p=0,007). Näo houve associaçäo entre a distribuiçäo do fluxo pulmonar com as avaliaçöes clínica e radiológica. Conclusäo: näo se evidenciou distribuiçäo de fluxo sangüíneo pulmonar com caraterística de expressar o padräo da relaçäo ventilaçäo-perfusäo em lactentes jovens, hospitalizados com bronquiolite viral aguda. Ocorreu apenas uma tendência de redirecionamento da distribuiçäo do fluxo sangüíneo para as regiöes pulmonares superiores