Central University of Venezuela
  • Caracas, Metropolitano, Venezuela
Recent publications
The study of the behavior of asphaltenes in solution has focused on their tendency to form aggregates and less importance has been given to describing and understanding what allows the formation of asphaltene aggregates that remain stably dispersed. Using molecular dynamics simulations, we calculated that the dipole moment of models for asphaltene aggregate tends to zero when the number of molecules in the aggregate tends to large values. In other words, such dipole moment cancellation would be an important contributor to the dispersion of these aggregates.
The aggregation and adsorption of asphaltenes in dilute solutions has been extensively studied and is now well established. At low concentrations, asphaltenes are mainly found in the form of aggregates of approximately 3 nm in size. One strategy to simplify the study of these systems has been to fractionate the asphaltenes into subfractions called A1 and A2. The nature of these subfraction aggregates, their behavior with the concentration and their interaction with other aggregates and surfaces remain under debate. This work presents experimental results on the aggregation and adsorption of asphaltenes and their subfractions A1 and A2 onto SiO2 nanoparticles from rice husks (RH-SiO2), and the evidence allows us to infer that the aggregates are in equilibrium in solution over a wide range of concentrations. The size distribution for each subfraction does not change with dilution but is sensitive to solvent media. Subfraction A1 has a very similar behavior to asphaltenes, while subfraction A2 tends to form larger aggregates. Larger aggregates more likely adsorb on surfaces than small aggregates. According to the results, the interaction of the aggregates in different solvents can be studied as a phase change phenomenon, where the aggregate can be considered a partially immiscible phase in a solvent. The theoretical principles are described, and a hypothesis is elaborated in these terms.
Discrimination against persons with disability is not just a relational phenomenon. It has a structural dimension that is equally oppressive. Structural discrimination can occur even in places and instances where individual discrimination may not be present. Structural discrimination is not always easily noticeable and thus cannot be legislated against easily. This study explored the lived experiences of structural discrimination as experienced by 16 middle-class persons with disability in Ghana. The participants shared experiences of simultaneous acceptance and limited access or in some cases rejection in educational institutions, places of work, religious spaces and the service industry. These experiences of structural discrimination happen because the social class positions of middle-class persons with disability qualify them to enter mainstream social, economic and political spaces but the stigma which their impairments elicit compromises their identities in these spaces, making their full integration into mainstream activities challenging. Corporeal differences ought not to be used as basis for denying access to resources and opportunities. Societies have to consciously work to identify structures that oppress persons with disability and inhibit their integration into mainstream activities. There is the need for the creation of an inclusive society that actively pursues the dismantling of exclusionary structures and normative systems within society.
Cancer remains strongly associated with morbidity and lethality posing a massive challenge to public health from decades. Thus, new interventions, effective and meaningful therapeutic approaches towards the treatment of cancer are urgently required. In this regard, nanotechnology offers an efficacious pharmacological application towards anticancer therapy. Therefore, the current study was aimed to develop Berberis aristata aqueous extract loaded gelatin lipid‐nanocarriers to explore their in vitro and in vivo antitumor properties. The extract loaded gelatin lipid nanoparticles were formulated by using double emulsion solvent evaporation method and physical characterization was performed using various techniques. Hydrodynamic diameter, zeta potential and polydispersity index (PDI) of GLN‐BA were observed as 322±7 nm, −31.49±4.85 mV and 0.397±0.102 mV, respectively. The extract was efficiently entrapped within the GLN (EE=79±11 %) and follow the diffusion type release mechanism. Moreover, transmission electron microscopy (TEM) demonstrated the spherical shaped smooth morphology of nanospheres. In vitro anticancer activity of GLN‐BA was performed by SRB assay and shown to demonstrate effective cytotoxicity (IC50=4.73±2.95 μg/mL) against MCF‐7 which was further quantitatively and qualitatively verified by flow cytometry, genotoxicity and DAPI staining. Induction of apoptotic bodies provides the evidence for apoptosis mediated cytotoxicity. Further, in vivo analysis on female mice was carried out to corroborate anticancer activity and was comparable to cisplatin. At 10th day, the GLN‐BA (10 mg/kg) prominently reduced the tumor volume to 35±11 % in consistent with cisplatin (3 mg/kg) which exhibited 41±5 % reduction. Moreover, molecular modeling analysis substantiates the stable nanoformulation encapsulating the BA bioactive constituent. Taken together, current findings supported the therapeutic effectiveness of BA encapsulated gelatin lipid nanoparticles towards breast cancer suggesting the use of medicinal plant as a prototype to treat tumor. The Figure depicts results of pharmacological testing (both in vitro and in vivo). In vitro SRB assay represents cell viability (%) and cell death (%) against human breast cancer cells (MCF‐7) representing the IC50 values for pure extract and GLN‐BA treated cells (left). In vivo antitumor assessment in an animal model (right)
Background Since 2015, the Global Technical Strategy (GTS) for Malaria 2016–2030 has been adopted by the World Health Organization (WHO) as a comprehensive framework to accelerate progress for malaria elimination in endemic countries. This strategy sets the target of reducing global malaria incidence and mortality rates by 90% in 2030. Here it is sought to evaluate Brazil’s achievements towards reaching the WHO GTS milestone in 2030. Considering the total number of new malaria cases in 2015, the main research question is: will Brazil reach the malaria elimination goal in 2030? Methods Analytical strategies were undertaken using the SIVEP-malaria official databases of the Brazilian Malaria Control Programme for the Brazilian Amazon region from 2009 to 2020. Spatial and time-series analyses were applied for identifying municipalities that support the highest numbers of malaria cases over the years. Forecast analysis was used for predicting the estimated number of new cases in Brazil in 2025–2050. Results Brazil has significantly reduced the number of new malaria cases in 2020 in comparison with 2015 in the states of Acre (− 56%), Amapá (− 75%), and Amazonas (− 21%); however, they increased in the states of Pará (156%), Rondônia (74%), and Roraima (362%). Forecast of the predicted number of new malaria cases in 2030 is 74,764 (95% CI: 41,116–141,160) in the Brazilian Amazon. Conclusions It is likely that Brazil will reduce the number of new malaria cases in the Brazilian Amazon in 2030 in relation to that in 2015. Herein forecast shows a reduction by 46% (74,754 in 2030 forecast/137,982 in 2015), but this reduction is yet far from the proposed reduction under the WHO GTS 2030 milestone (90%). Stable and unbeatable transmission in the Juruá River Valley, Manaus, and Lábrea still support endemic malaria in the Brazilian Amazon. Today’s cross-border malaria is impacting the state of Roraima unprecedently. If this situation is maintained, the malaria elimination goal (zero cases) may not be reached before 2050. An enhanced political commitment is vital to ensure optimal public health intervention designs in the post-2030 milestones for malaria elimination. Graphical Abstract
Climate change affects the physiology of cocoa; however, research under high temperature and elevated [CO2] is scant. It is important to consider the physiological response of cocoa to the interaction of these environmental variables and thus generate an accurate prediction of how this crop will respond to climate change. In order to know whether elevated [CO2] leads to an increase in photosynthetic rate (A) and water use efficiency (WUE), thereby decreasing the negative impact of elevated temperature on physiology of cocoa (Theobroma cacao L), gas exchange, diurnal carbon:water balance (DCWB), photochemical activity of PSII, response curves of A to intercellular [CO2] (A/Ci curves) and growth were determined in two high temperature (T) sensitive cocoa clones (INIFAP-8 and Neocriollo) cultivated in controlled growth chambers for 100 days. The chamber environmental conditions were low [CO2]- low T (LCLT; 400 µmol CO2 mol⁻¹ and 30 °C); high [CO2]- high T (HCHT; 1200 µmol CO2 mol⁻¹ and 40 °C); high [CO2]- low T (HCLT; 1200 µmol CO2 mol⁻¹ and 30 °C) and low [CO2]- high T (LCHT; 400 µmol CO2 mol⁻¹ and 40 °C). A significant increase in A, WUE, DCWB and growth was found in both clones grown at high [CO2]. However, high T (40 °C) considerably decreased the physiology of both clones but its impact was significantly mitigated by elevated [CO2]. The results show that the physiological effects generated by elevated [CO2] could reduce the negative impact of increased temperatures, increasing the tolerance range of cocoa in the future.
The plasma membrane and autoinhibited Ca²⁺-ATPases contribute to the Ca²⁺ homeostasis in a wide variety of organisms. The enzymatic activity of these pumps is stimulated by calmodulin, which interacts with the target protein through the calmodulin-binding domain (CaMBD). Most information about this region is related to all calmodulin modulated proteins, which indicates general chemical properties and there is no established relation between Ca²⁺ pump sequences and taxonomic classification. Thus, the aim of this study was to perform an in silico analysis of the CaMBD from several Ca²⁺-ATPases, in order to determine their diversity and to detect specific patterns and amino acid selection in different species. Patterns related to potential and confirmed CaMBD were detected using sequences retrieved from the literature. The occurrence of these patterns was determined across 120 sequences from 17 taxonomical classes, which were analyzed by a phylogenetic tree to establish phylogenetic groups. Predicted physicochemical characteristics including hydropathy and net charge were calculated for each group of sequences. 22 Ca²⁺-ATPases sequences from animals, unicellular eukaryotes, and plants were retrieved from bioinformatic databases. These sequences allow us to establish the Patterns 1(GQILWVRGLTRLQTQ), 3(KNPSLEALQRW), and 4(SRWRRLQAEHVKK), which are present at the beginning of putative CaMBD of metazoan, parasites, and land plants. A pattern 2 (IRVVNAFR) was consistently found at the end of most analyzed sequences. The amino acid preference in the CaMBDs changed depending on the phylogenetic groups, with predominance of several aliphatic and charged residues, to confer amphiphilic properties. The results here displayed show a conserved mechanism to contribute to the Ca²⁺ homeostasis across evolution and may help to detect putative CaMBDs. Graphical Abstract
This paper deals about a proposal for the remediation of soils and groundwater contaminated with hydrocarbons in a tropical aquifer, due to leaks from underground tanks in a gas station in Venezuela. The hydrocarbon measured values such as TPHs (Total Petroleum Hydrocarbons) and BTEX (Benzene, Toluene, Ethylbenzene, Xylenes) in soils and ground water exceeded the international standards. The remediation proposal was designed using kinetic models from the modified Monod equation for two coupled bioreactors, using as design variable for the Chemical Oxygen Demand (COD). For soil treatment, the sequence was formed by Soil-Slurry Sequencing Batch Reactor (SS-SBR)and Upflow Anaerobic Filter separate in three phases (UAF-3SS) operating for 80% and 99% of COD removal, respectively. For groundwater treatment, it was set the SBR-UAF-3SS sequence performs a COD removal of 60% and 99%, respectively.
Skeletal muscle, the main metabolic engine in the body of vertebrates, is endowed with great plasticity. The association between skeletal muscle plasticity and two highly prevalent health problems: renal dysfunction and obesity, which share etiologic links as well as many co-morbidities, is a subject of great relevance. It is important to know how these alterations impact on the structure and function of skeletal muscle because the changes in muscle phenotype have a major influence on the quality of life of the patients. This literature review aims to discuss the influence of a non-traditional axis involving kidney, bone, and muscle on skeletal muscle plasticity. In this axis, the kidneys play a role as the main site for vitamin D activation. Renal disease leads to a direct decrease in 1,25(OH) 2 -vitamin D, secondary to reduction in renal functional mass, and has an indirect effect, through phosphate retention, that contributes to stimulate fibroblast growth factor 23 (FGF23) secretion by bone cells. FGF23 down-regulates the renal synthesis of 1,25(OH) 2 -vitamin D and up-regulates its metabolism. Skeletal production of FGF23 is also regulated by caloric intake: it is increased in obesity and decreased by caloric restriction, and these changes impact on 1,25(OH) 2 -vitamin D concentrations, which are decreased in obesity and increased after caloric restriction. Thus, both phosphate retention, that develops secondary to renal failure, and caloric intake influence 1,25(OH) 2 -vitamin D which in turn plays a key role in muscle anabolism.
We use 1.5 years of continuous recordings from an amphibious seismic network deployment in the region of northeastern South America and the southeastern Caribbean to study the crustal and uppermost mantle structure through a joint inversion of surface-wave dispersion curves determined from ambient seismic noise and receiver functions. The availability of both ocean bottom seismometers (OBSs) and land stations makes this experiment ideal to determine the best processing methods to extract reliable empirical Green's functions (EGFs) and construct a 3D shear velocity model. Results show EGFs with high signal-to-noise ratio for land–land, land–OBS and OBS–OBS paths from a variety of stacking methods. Using the EGF estimates, we measure phase and group velocity dispersion curves for Rayleigh and Love waves. We complement these observations with receiver functions, which allow us to perform an H-k analysis to obtain Moho depth estimates across the study area. The measured dispersion curves and receiver functions are used in a Bayesian joint inversion to retrieve a series of 1D shear-wave velocity models, which are then interpolated to build a 3D model of the region. Our results display clear contrasts in the oceanic region across the border of the San Sebastian–El Pilar strike-slip fault system as well as a high-velocity region that corresponds well with the continental craton of southeastern Venezuela. We resolve known geological features in our new model, including the Espino Graben and the Guiana Shield provinces, and provide new information about their crustal structures. Furthermore, we image the difference in the crust beneath the Maturín and Guárico sub-basins.
Latitudinal distances between the two equatorial ionization anomaly (EIA) crests in total electron content (TEC) of global ionosphere map (GIM) are used to derive the daily dynamo eastward electric field by comparing the eastward electric field calculated by ROCSAT‐1 vertical ion velocity in four seasons. The electric fields derived by the EIA crests of GIM TEC, ROCSAT‐1 ion velocity, and the incoherent scatter radar (ISR) observations at Jicamarca are generally in good agreement in longitudes and seasons. Meanwhile, the electric fields derived by the EIA crests agree well with those by ROCSAT‐1, FORMOSAT‐7/COSMIC‐2, and Jicamarca ISR on individual days. A long‐term study of the GIM‐TEC crest distance reveals obvious solar activity dependency of the daily dynamo electric field during 1999–2020. These agreements confirm that the EIA crest can be used to derive the daily eastward dynamo electric field and the associated vertical ion velocity which is responsible to the strength of equatorial plasma fountain and the latitudinal extend of the EIA. Moreover, the vertical ion velocity derived by the GIM‐TEC crest distance is further used to improve the SAMI2 model for space weather applications.
Among influence factors of slope stability, rainfall is the most triggering factor. When rainwater flows through the slip surface, it will cause slope movement. This paper studies the slope movement in Kalibawang irrigation channel at km. 15+900, which induced failure of the irrigation channel and other surrounding structures. The slope movement was modelled as coupled stress-pore water pressure analysis using SIGMA/W. Satellite-based rainfall data of Tropical Rainfall Measuring Mission (TRMM) was collected from 1 July to 30 August 2017. The numerical model was validated with the field monitoring for deformation and pore water pressure to obtain a reliable soil parameter. Several attempts have been made to obtain an acceptable of E parameter by determining the smallest root mean square error (RMSE) value of deformation and larger coefficient of relation (R ² ). The numerical model has been extended to evaluate the slope stability after remedial work using piles. Six rainfall scenario were applied to model. The analysis concludes that the piling works increases the slope stability under several rainfall scenarios, which is indicated by increase in factor of safety.
In the developing world, most animal farmhouses dispose of their wastewater without treatment and that creates conditions for the spread of diseases. To discourage this practice, there is the need to provide relatively simpler wastewater treatment options. Thus, this research work sought to optimise the chemical oxygen demand (COD) removal efficiency of a simple anaerobic digester by determining the optimum concentrations of rhamnolipid biosurfactant and potassium phosphate buffer needed to make the anaerobic digester remove COD efficiently. The central composite design was used for the optimization study. In the one factor at a time experiment, increasing the concentration of the potassium phosphate buffer from 1.07 g/l K 2 HPO 4 + 0.53 g/l KH 2 PO 4 to 1.37 g/l K 2 HPO 4 + 0.83 g/l KH 2 PO 4 increased the COD removal efficiency of the anaerobic digester from 19.3 to 24.7%. Also, increasing the concentration of rhamnolipid from 80 to 320 mg/l increased the efficiency of the digester from 24.2 to 26%. The percentage COD removal was highly improved (> 85%) in the optimisation study when both rhamnolipid and buffer were combined at high levels (+ 1). The model built from the central composite design reflected a good fit of the data obtained with R 2 of 82.5% and a p value of 0.000. This study therefore demonstrated that a simple anaerobic digester can be used to remove COD in wastewater by optimising the concentrations of rhamnolipid and potassium phosphate buffers in the treatment system.
Background Leishmaniasis is a tropical disease caused by protozoan parasites of the genus Leishmania. Mucosal leishmaniasis has been described as secondary to the cutaneous form; however, isolated mucosal involvement can also occur. Specifically, mucosal leishmaniasis of the lip is poorly described and its diagnosis challenges clinicians. Methods We herein report a case of mucosal leishmaniasis affecting the lower lip without cutaneous involvement in a 20-year-old Venezuelan man. The patient had no relevant past medical history. Clinically, a mass-like lesion with ulcerations and crusts was observed. Results Microscopically, the lesion was composed of granulomatous inflammation along with macrophages containing intracytoplasmic inclusions similar to round-shaped Leishmania. The species Leishmania (Viannia) braziliensis was confirmed. Treatment with meglumine antimonate was effective. The lesion healed satisfactorily, and no side effects or recurrences were observed. Conclusion Clinicians should be aware of isolated forms of mucosal leishmaniasis of the lip, even in cases where the cutaneous lesion is undetected or clinically manifests as self-limiting. Knowing the endemic areas in the scenario of the dynamics of the ecoepidemiology of leishmaniasis is also essential for surveillance and counselling of the population.
Many women of reproductive age in sub Saharan Africa are not utilizing any contraceptive method which is contributing to the high burden of maternal mortality. This study determined the prevalence, trends, and the impact of exposure to family planning messages (FPM) on contraceptive use (CU) among women of reproductive age in sub-Saharan Africa (SSA). We utilized the most recent data from demographic and health surveys across 26 SSA countries between 2013 and 2019. We assessed the prevalence and trends and quantified the impact of exposure to FPM on contraceptive use using augmented inverse probability weighting with regression adjustment. Sensitivity analysis of the impact estimate was conducted using endogenous treatment effect models, inverse probability weighting, and propensity score with nearest-neighbor matching techniques. The study involved 328,386 women of reproductive age. The overall prevalence of CU and the percentage of women of reproductive age in SSA exposed to FPM were 31.1% (95% CI 30.6–31.5) and 38.9% (95% CI 38.8–39.4) respectively. Exposure to FPM increased CU by 7.1 percentage points (pp) (95% CI 6.7, 7.4; p < 0.001) among women of reproductive age in SSA. The impact of FPM on CU was highest in Central Africa (6.7 pp; 95% CI 5.7–7.7; p < 0.001) and lowest in Southern Africa (2.2 pp; 95% CI [1.3–3.0; p < 0.001). There was a marginal decline in the impact estimate among adolescents (estimate = 6.0 pp; 95% CI 5.0, 8.0; p < 0.001). Exposure to FPM has contributed to an increase in CU among women of reproductive age. Programs that are geared towards intensifying exposure to FPM through traditional media in addition to exploring avenues for promoting the appropriate use of family planning method using electronic media remain critical.
Pectin is a high molecular weight polymer which is present in virtually all plants where it contributes to the cell structure. Pectin is a high valuable food ingredient widely used as a gelling agent and thickening agent with limited use in the pharmaceutical industry. The objective of this study is to evaluate the suspending properties of pectin from watermelon rind. Tragacanth was used as a standard suspending agent to which the suspending properties of pectin from watermelon rinds were compared with. The extracted pectin was subjected to phytochemical and physiochemical characterization for its safety and suitability to use as a suspending agent. Paracetamol suspensions were formulated using tragacanth concentrations of 0.5% w/v, 1% w/v, and 2% w/v and compared with paracetamol suspensions containing the same concentrations of watermelon pectin. The suspensions were all tested for their pH, sedimentation rate, sedimentation volume, flow rate, and ease of redispersibility over a period of 4 weeks. At the end of the 4-week period, all formulated suspensions had no changes in their pH values. Suspensions containing the extracted pectin had a lower rate of sedimentation and ease of redispersibility compared to that of tragacanth. In addition, their sedimentation volumes as well as flow rates were comparable to that of the tragacanth formulations. Ultimately, pectin from watermelon rind can serve as a suitable alternative to tragacanth in formulation of pharmaceutical suspensions.
Introduction Non-Hodgkin lymphomas (NHL) are the most frequently recognized entities among lymphoproliferative syndromes and rank fifth among neoplasms not associated with gender. There is scarce information on the clinical characteristics of the most frequent NHL, and no data on treatment regimens and their outcomes in Latin America. Although many factors affect a patient’s possibilities of receiving treatment, the annual income per person/country is pivotal in Latin America. Aim We present the clinical characteristics, risk groups, and treatment regimens of the three most frequent lymphoma subtypes in Latin America [diffuse large B-cell lymphoma (DLBCL), follicular lymphoma (FL), and peripheral T-cell lymphoma (PTCL)], based on the data collected by the largest study group of lymphoproliferative diseases in Latin America: The Latin American Study Group of Lymphoproliferative Disease [Grupo de Estudio de Linfoproliferativos de Latino America (GELL)]. Outcomes The most frequent treatment regimen for B-cell lymphomas is immunochemotherapy (R-CHOP ≥70%), and CHOP for PTCL. Survival is similar to that reported by industrialized nations. We have no solid data on the results of treatment with salvage regimens nor stem cell transplantation in refractory/ relapsed NHL. Conclusion In Latin America, the same treatment regimens are used as in highly developed countries, although we lack the necessary technology to apply CAR T-cell therapies or a network of trials sponsored by the pharmaceutical industry.
Steroid injections in joints are commonly administered for the management of inflammatory or degenerative conditions. There is substantial controversy as to whether to continue warfarin when undertaking joint injection or aspiration. To assess the rate of bleeding complications in patients on warfarin undergoing joint injection/aspiration. Systematic review and meta-analysis. A literature search of 3 online databases was conducted by 2 reviewers using the Cochrane methodology for systematic reviews. Eligibility criteria were any study that reported bleeding complication rates in adult patients on warfarin undergoing a joint injection/aspiration whilst taking warfarin anticoagulation. Studies reporting on less than 5 patients were excluded. Meta-analysis was conducted using a random effects model. The search of databases resulted in a total of 1547 articles. After screening, 8 articles were deemed suitable for inclusion in the analysis, involving 871 injection/aspiration procedures. There were only 5 reported cases of bleeding. On meta-analysis the estimated bleeding complication rate was 1.5% (95% CI 0.5–4.5%). This meta-analysis shows that it is safe to perform joint injection and aspiration in patients on warfarin without routine prior testing of INR. Level of evidence: Level 4.
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2,610 members
Miguel Angel Briceno Gil
  • Instituto de Filosofía
Alejandro Salvador
  • Departamento de Produccion and Industria Animal
Thais del-Valle Diaz
  • Instituto de Reproducción Animal
Maria L Serrano
  • Faculty of Pharmacy
Ciudad Universitaria, Los Chaguaramos, 1051, Caracas, Metropolitano, Venezuela
Head of institution
Dra Cecilia García