Resistive Switching and Charge Transport in Laser-Fabricated Graphene Oxide Memristors: A Time Series and Quantum Point Contact Modeling Approach.

This work investigates the sources of resistive switching (RS) in recently reported laser-fabricated graphene oxide memristors by means of two numerical analysis tools linked to the Time Series Statistical Analysis and the use of the Quantum Point Contact Conduction model. The application of both numerical procedures points to the existence of a filament connecting the electrodes that may be interrupted at a precise point within the conductive path, resulting in resistive switching phenomena. These results support the existing model attributing the memristance of laser-fabricated graphene oxide memristors to the modification of a conductive path stoichiometry inside the graphene oxide.

Necrosis grasa subcutánea en un recién nacido y sus complicaciones / Subcutaneous fat necrosis in newborn and its complications

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CYP1A1, CYP2E1 and GSTM1 genetic polymorphisms. The effect of single and combined genotypes on lung cancer susceptibility in Chilean people.

CYP1A1, CYP2E1 and GSTM1 polymorphisms were evaluated in Chilean healthy controls and lung cancer patients. In the Chilean healthy group, frequencies of CYP1A1 variant alleles for MspI (m2 or CYP1A1*2A) and ile/val (val or CYP1A1*2B) polymorphisms were 0.25 and 0.33, respectively. Frequencies of variant alleles C (CYP2E1*6) and c2 (CYP2E1*5B) for CYP2E1 were 0.21 and 0.16, respectively and frequency for GSTM1(-) was 0.24. The presence of variant alleles for GSTM1, MspI and Ile/val polymorphisms was more frequent in cases than in controls. However, frequencies for the c2 and C alleles were not significantly different in controls and in cases. The estimated relative risk for lung cancer associated to a single mutated allele in CYP1A1, CYP2E1 or GSTM1 was 2.41 for m2, 1.69 for val, 1.16 for C, 0.71 for c2 and 2.46 for GSTM1(-). The estimated relative risk was higher for individuals carrying combined CYP1A1 and GSTM1 mutated alleles (m2/val, OR=6.28; m2/GSTM1(-), OR=3.56) and lower in individuals carrying CYP1A1 and CYP2E1 mutated alleles (m2/C, OR=1.39; m2/c2, OR=2.00; val/C, OR=1.45; val/c2, OR=0.48; not significant). The OR values considering smoking were 4.37 for m2, 4.05 for val, 3.47 for GSTM1(-), 7.38 for m2/val and 3.68 for m2/GSTM1(-), higher values than those observed without any stratification by smoking. Taken together, these findings suggest that Chilean people carrying single or combined GSTM1 and CYP1A1 polymorphisms could be more susceptible to lung cancer induced by environmental pollutants such as polycyclic aromatic hydrocarbons.

Influence of copper-(II) on colloidal carbon-induced Kupffer cell-dependent oxygen uptake in rat liver: relation to hepatotoxicity.

Formation of reactive O2 species in biological systems can be accomplished by copper-(II) (Cu2+) catalysis, with the consequent cytotoxic response. We have evaluated the influence of Cu2+ on the respiratory activity of Kupffer cells in the perfused liver after colloidal carbon infusion. Studies were carried out in untreated rats and in animals pretreated with the Kupffer cell inactivator gadolinium chloride (GdCl3) or with the metallothionein (MT) inducing agent zinc sulphate, and results were correlated with changes in liver sinusoidal efflux of lactate dehydrogenase (LDH) as an index of hepatotoxicity. In the concentration range of 0.1-1 microM, Cu2+ did not modify carbon phagocytosis by Kupffer cells, whereas the carbon-induced liver O2 uptake showed a sigmoidal-type kinetics with a half-maximal concentration of 0.23 microM. Carbon-induced O2 uptake occurred concomitantly with an increased LDH efflux, effects that were significantly correlated and abolished by GdCl3 pretreatment or by MT induction. It is hypothesized that Cu2+ increases Kupffer cell-dependent O2 utilization by promotion of the free radical processes related to the respiratory burst of activated liver macrophages, which may contribute to the concomitant development of hepatocellular injury.

[Modification of the lipid profile of human placenta by moderate maternal undernutrition]. / Modificación del perfil lipídico de la placenta humana por efecto de la desnutrición materna moderada.

The lipid composition of human placenta phospholipids, coming from 9 undernourished women that gave birth to low weight newborns and 9 well nourished women, was analyzed using gas-liquid chromatography. Phospholipids of placentas coming from undernourished women, when compared to well nourished women, had significantly lower amounts of w-6 and w-3 fatty acids (40.1 +/- 1.5 vs 42.4 +/- 1.4 and 6.0 +/- 0.7 vs 7.1 +/- 1.3% respectively). The calculated mean melting point was higher in plancetas coming from undernourished women. It these women, the low content of polyunsaturated fatty acids and its replacement by short chain fatty acids was not able to balance the high mean melting points. The relative deficiency of essential fatty acids, the low saturation index and the high mean melting point of undernourished women's placental phospholipids, may suggest a lower membrane fluidity and a subnormal essential fatty acid content of fetal organs, that are essential for normal growth and development.

[The effect of dietary Omega 6 polyunsaturated fatty acids on the activity of enzymes associated with liver mitochondrial and placental function in rats]. / Influencia del contenido de ácidos grasos poliinsaturados Omega 6 dietéticos, en la actividad de enzimas asociadas a la función de la membrana mitocondrial de hígado y placenta de ratas.

Female virgin rats, Wistar strain, divided into three groups of 18 each, were fed either a diet containing 45% of calories as fat (45 g%), the second received low-fat diet (15 g%), before and throughout pregnancy, and the third served as control. For both dietary fat levels, the polyunsaturated to saturated fatty acid (P/S) ratio was adjusted by substitution of saturated fatty acids for corn oil, to provide P/S of 2.0. The control group was fed a diet containing 30% of calories, as fat, with a P/S ratio of 1.0. Rats were sacrificed by decapitation 20 days after mating: fetuses, placenta and liver were then removed and weighed. Liver and placenta mitochondria were isolated. Phospholipids were extracted from mitochondrial membranes, and fatty acid tail composition was determined. Cytochrome c oxidase (a3) and rotenone-insensitive-NADH cytochrome c reductase (NADH cyt c red) in mitochondria subfractions were also assayed. The high-fat diet (45 g%) resulted in an increase in both liver and placental a3, but NADHcyt-c-red, activity did not change. The low fat diet (15 g%) reduced the activity of insensitive rotenone-NADH cytochrome c reductase. The fetal weight of the mothers fed the high-fat diet was higher (p less than 0.001) than in the other groups. No difference in fetal weight was observed between the pregnant groups fed 30% or 15% of calories (fat diets). These results suggest that changes in the fatty acid mitochondrial phospholipids which reflects the composition of dietary fat can result in changes in lipid-dependent function of integral membrane-bound enzymes. Therefore, it can be postulated that the increase of membrane fatty acid Omega 6 enhanced the a3 enzyme activity, which correlated with an increase in fetal growth.

[Gamma-glutamyltranspeptidase activity and glutathione content in the mammary gland during the processes of pregnancy and lactation in chronically malnourished rats]. / Actividad de gama glutamil transpeptidasa y contenido de glutatión en la glandula mamaria durante el progreso de la preñex y la lactancia en ratas cronicamente desnutridas.

The influence of early and chronically dietary protein and energy restriction on gamma glutamyl transpeptidase (GGTP: E.C.2.3.2.2.) activity of the mammary gland of pregnant and lactating rats, was studied. Rats fed a restricted amount of a 25% casein diet throughout gestation and lactation decreased mammary gland weight, DNA, and protein content. The GGTP activity in the mammary gland of the malnourished group was significantly decreased during all of the experimental trial period, and a decrease of offspring weight gain was also observed in that group. The inhibition of GGTP activity in the mammary gland caused by effects of maternal protein and energy undernutrition, could have depressed mammary uptake of amino acids, suggesting a reduced milk protein content and/or milk output.

[Energy metabolism during placental development in rats--effect of chronic maternal malnutrition]. / Metabolismo energético durante el desarrollo de la placenta en ratas--effecto de la desnutrición materna crónica.

The effect of maternal malnutrition on the energy metabolism of the developing rat placenta, related to fetal growth, was studied. Female virgin rats of the Wistar strain were fed restricted amounts of 25% casein diet, from puberty and throughout pregnancy. According to results, a significant decrease occurred in the activity of adenylate kinase, as well as a significant increase in the energy charge of the adenylate system (ATP, ADP), per gram of DNA of placental tissue near term, in the malnourished group. The data suggest that the significant increase of energy charge (ATP + 1/2 ADP:/ATP + ADP + AMP) of the placenta in the malnourished group, is the consequence of an inhibition of the reactions controlling ATP-consuming process, such as macromolecular synthesis pathways and active transport of substrates near term. This coincides with the simultaneous and significant decrease in fetal growth in this group.

[Lipid composition of the placenta of rats with protein restriction and deficiency of essential fatty acids]. / Composición lipídica de la placenta de ratas con restricción de proteínas y deficiencia de ácidos grasos esenciales.

The influence of diet restriction and EFA deficiency during pregnancy in the rat on the lipid and phospholipids composition of the placenta was investigated. Female virgin albino Wistar rats weighing 130 +/- 4 g, were assigned to three equivalent groups. Prior mating and during pregnancy each group of rats received the following regimen: Animals in the Control Group (C) were fed a 25% casein diet in ad libitum quantities; the dietary Restricted Group (D) received the same control diet in amounts calculated to approximate 50% (g/100 g rat) of the intake of group C; the Deficient and Restricted Group (DD) rats were fed a restricted amount of EFA deficient diet. On the 21st day of gestation pregnant animals were sacrificed. The foetuses and placentae obtained by caesarium section were isolated and weighed. A 50% food restriction before and during pregnancy resulted in a significant decrease in phospholipid contents (p less than 0.05); severe EFA deficiency superimposed to 50% food restriction, moreover induced significant changes in the fatty acid pattern of phospholipids, decreasing n3 and n6 fatty acids and increasing eicosatrienoic acid. There was an accumulation of triglycerides in the placenta of rats fed on the EFA deficient diet. In the two restricted groups fetal weight was reduced, but although in the DD group, placental weight was not affected, litter size was dramatically reduced.