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In this paper we study the structure and phase behavior of binary mixtures of charged particles at low ionic strength. Due to the large size asymmetry between both species, light scattering measurements give us access only to the partial static structure factor that corresponds to the big particles. We observe that the addition of small charged colloids produces a decrease of the main peak of the measured static structure factor and a shift to larger scattering vector values. This finding is in agreement with theory based on integral equations with the Hypernetted-Chain Closure (HNC) relation. The effective interaction between two big particles due to the presence of small particles is obtained by a HNC inversion scheme and used in numerical simulations that adequately reproduce the experiments. We find that the presence of small particles induces an electrostatic depletion screening among the big colloids, creating around them an exclusion zone for the small charged colloids greater than that caused in the case of neutral small colloids, which in turn augments the depletion effect.
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BACKGROUND: Paraoxonase 1 (PON1) and glutathione S-transferases (GSTs) are involved in the biotransformation of xenobiotics. Variation in the enzyme concentration and activity suggests individual differences for the degree of protection against oxidative stress. AIM: This study analysed the distribution of SNPs Q192R, L55M (PON1) and variants in GSTM1 and GSTT1 genes in a population from Southeastern Mexico. SUBJECTS AND METHODS: One hundred and fifty-one Mexican Mestizo healthy volunteers were included. PON1 polymorphisms were determined by Taqman allele discrimination real time-PCR, whereas GSTM1 and GSTT1 genes were determined with a multiplex PCR-based method. RESULTS: All genotypes were in Hardy-Weinberg equilibrium, except for GSTM1. The genotypic distributions of Q192R and L55M were 22% QQ, 48% QR, 30% RR, 62% LL, 34% LM and 4% MM, respectively, whereas the allele frequencies were 0.46 (Q), 0.54 (R), 0.79 (L) and 0.21 (M). The most frequent haplotype was R/L (46.7%). It was found that 31% and 9% of the individuals had the GSTM1 and GSTT1 null genotype, respectively. The frequency of the combined null genotype GSTM1*0/GSTT1*0 was 4.64%. CONCLUSION: The results showed that the frequencies of polymorphisms of PON1, GSTM1 and GSTT1 in the Yucatán population differ to those observed in other ethnic groups and provide useful data for epidemiological studies.
Assuntos
Arildialquilfosfatase/genética , Variação Genética , Glutationa Transferase/genética , Estresse Oxidativo/genética , Feminino , Frequência do Gene/genética , Haplótipos/genética , Humanos , Masculino , México , FilogeniaRESUMO
BACKGROUND: Current recommendations for the anesthetic management of placenta accreta support a conservative approach with neuraxial anesthesia and uterine artery embolization. These are based on case series from experienced centers in developed countries. The aim of this study was to describe the anesthetic management of placenta accreta in a low-resource setting. METHODS: A retrospective case note review was performed. From 1 August 2006 to 31 July 2011 placentas from cases of suspected placenta accreta were reassessed histologically to confirm the diagnosis. Patient charts were reviewed and information on anesthetic technique, monitoring, blood transfusion, maternal and fetal outcomes was extracted. RESULTS: Thirty-nine cases were identified. Mean (± SD) maternal age was 33 ± 5.4 years. Hysterectomy was performed at the time of cesarean section in all cases. Thirty-four patients received neuraxial anesthesia, of whom 15 required conversion to general anesthesia. Invasive blood pressure monitoring was used in all patients and a central venous catheter was inserted in 33 cases. Complications associated with monitoring occurred in five patients. Median [IQR] blood loss was 2000 [1100-2700] mL and the median [IQR] number of units of red blood cell transfused was 2 [0-6]. Vasoactive medication was used in 14 patients and 15 patients were transferred to the intensive care unit postoperatively. No maternal or newborn deaths occurred. CONCLUSION: A multidisciplinary approach can prove valuable when placenta accreta is suspected before delivery. In low-resource settings, lack of interventional radiology services and prenatal diagnostic capability may have an impact on anesthetic management in patients with placenta accreta. However, other than greater blood loss, our study demonstrated that good maternal and neonatal outcomes are possible in spite of limited resources.
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Anestesia/métodos , Cesárea , Países em Desenvolvimento , Placenta Acreta/cirurgia , Adulto , Anestesia Geral/estatística & dados numéricos , Colômbia , Feminino , Recursos em Saúde , Humanos , Histerectomia/estatística & dados numéricos , Gravidez , Estudos Retrospectivos , Adulto JovemRESUMO
We investigate dynamic light scattering by non-ergodic turbid media with an adapted version of the method proposed by Pusey and van Megen [Physica A 157, 705 (1989)]. Our formulation follows the derivation of the original method by extending it to the three dimensional cross-correlation scheme (3DDLS). The main finding is an expression to obtain the dynamic structure factor from light scattering that takes into account the system turbidity and the peculiarities of the 3D geometry. From 3DDLS measurements in well-controlled solid-like systems of different turbidity, we confirm that our results can be interpreted reasonably well by the theoretical approach described here. Good agreement is found with earlier reported results on similar systems.