Search tips
Search criteria

Results 1-11 (11)

Clipboard (0)

Select a Filter Below

Year of Publication
Document Types
1.  A closer look at the operating definition of protein recovery in capillary electrophoresis 
Electrophoresis  2013;34(8):1141-1147.
Analyte recovery is an important figure to assess protein adsorption on fused-silica capillaries. In 1991 Regnier and coworkers estimated recovery by assuming the loss of analyte from adsorption and thus the decrease in peak area measured by two detectors to be proportional to the length of the capillary section between them. In this report we closely examine this concept and its adaptation to commercial CE instruments to determine protein recovery. We hypothesize that, once a steady-state migration is reached, protein adsorption is a first order process with respect to protein concentration and surface density of adsorbing sites. This hypothesis is shown to be valid over a reasonably wide range of capillary effective length and, as a result, protein recovery decreases exponentially with the migrated distance. However, unlike the traditional recovery figure obtained through a conventional spike process, protein recovery measured by this approach does not have the same merit since it is strongly dependent from capillary dimensions and applied electric field. Nevertheless, protein recovery and the slope of the logarithmic protein peak area vs. length plot are useful figures to compare protein adsorption on different capillary surfaces. Several literature reports dealing with the application of Regnier concept to calculate protein recovery are discussed.
PMCID: PMC3753406  PMID: 23400851
Capillary electrophoresis; Protein recovery; Silica surface
2.  Prevalence and Diversity of Bartonella spp. in Bats in Peru 
Bartonella infections were investigated in bats in the Amazon part of Peru. A total of 112 bats belonging to 19 species were surveyed. Bartonella bacteria were cultured from 24.1% of the bats (27/112). Infection rates ranged from 0% to 100% per bat species. Phylogenetic analyses of gltA of the Bartonella isolates revealed 21 genetic variants clustering into 13 divergent phylogroups. Some Bartonella strains were shared by bats of multiple species, and bats of some species were infected with multiple Bartonella strains, showing no evident specific Bartonella sp.–bat relationships. Rarely found in other bat species, the Bartonella strains of phylogroups I and III discovered from the common vampire bats (Desmodus rotundus) were more specific to the host bat species, suggesting some level of host specificity.
PMCID: PMC3435358  PMID: 22826480
3.  Adenovirus Respiratory Tract Infections in Peru 
PLoS ONE  2012;7(10):e46898.
Currently, there is a paucity of data regarding human adenovirus (HAdv) circulation in Andean regions of South America. To address this shortcoming, we report the clinical, phylogenetic, and epidemiologic characteristics of HAdv respiratory tract infection from a large sentinel surveillance study conducted among adults and children in Peru.
Methods/Principal Findings
Oropharyngeal swabs were collected from participants visiting any of 38 participating health centers, and viral pathogens were identified by immunofluorescence assay in cell culture. In addition, molecular characterization was performed on 226 randomly selected HAdv samples. Between 2000 and 2010, a total of 26,375 participants with influenza-like illness (ILI) or severe acute respiratory infection (SARI) were enrolled in the study. HAdv infection was identified in 2.5% of cases and represented 6.2% of all viral pathogens. Co-infection with a heterologous virus was found in 15.5% of HAdv cases. HAdv infection was largely confined to children under the age of 15, representing 88.6% of HAdv cases identified. No clinical characteristics were found to significantly distinguish HAdv infection from other respiratory viruses. Geographically, HAdv infections were more common in sites from the arid coastal regions than in the jungle or highland regions. Co-circulation of subgroups B and C was observed each year between 2006 and 2010, but no clear seasonal patterns of transmission were detected.
HAdv accounted for a significant fraction of those presenting with ILI and SARI in Peru and tended to affect the younger population disproportionately. Longitudinal studies will help better characterize the clinical course of patients with HAdv in Peru, as well as determine the role of co-infections in the evolution of illness.
PMCID: PMC3466214  PMID: 23056519
4.  Evidence of Rabies Virus Exposure among Humans in the Peruvian Amazon 
In May of 2010, two communities (Truenococha and Santa Marta) reported to be at risk of vampire bat depredation were surveyed in the Province Datem del Marañón in the Loreto Department of Perú. Risk factors for bat exposure included age less than or equal to 25 years and owning animals that had been bitten by bats. Rabies virus neutralizing antibodies (rVNAs) were detected in 11% (7 of 63) of human sera tested. Rabies virus ribonucleoprotein (RNP) immunoglobulin G (IgG) antibodies were detected in the sera of three individuals, two of whom were also seropositive for rVNA. Rabies virus RNP IgM antibodies were detected in one respondent with no evidence of rVNA or RNP IgG antibodies. Because one respondent with positive rVNA results reported prior vaccination and 86% (six of seven) of rVNA-positive respondents reported being bitten by bats, these data suggest nonfatal exposure of persons to rabies virus, which is likely associated with vampire bat depredation.
PMCID: PMC3414554  PMID: 22855749
5.  Prevalence of Anaemia and Evaluation of Transferrin Receptor (sTfR) in the Diagnosis of Iron Deficiency in the Hospitalized Elderly Patients: Anaemia Clinical Studies in Chile 
Anemia  2012;2012:646201.
Iron constitutes the most prevalent nutritional deficiency worldwide. In Chile, anaemia epidemiological data is scarce, evaluating mainly children and women. Our objective was to determine prevalence of anaemia in an inpatient elderly population (≥60 years) and assess the usefulness of sTfR levels analyzed by other authors as a good predictor in the differential diagnosis of iron deficiency anaemia and anaemia of chronic disease. Method. We studied medical patients admitted at Hospital of Valdivia (HV), Chile, in a 2month period. World Health Organization criteria were used for anaemia. Results. 391 patients were hospitalized, average age 62.5 years, 247 elderly and 99 of which had anaemia. Anaemia was normocytic in 88.8%, and we observed: low serum iron in 46.3%, low ferritin 10.1%, high TIBC 2%, low % transferrin saturation (Tsat) 40%, and high sTfR 25%. Conclusions. As a first figure known in Chile, the prevalence of anaemia in the elderly inpatient was 40.1%. Our findings encourage us to promote the implementation of sTfR determination in the clinical setting to analyze the state of erythropoiesis in patients with chronic diseases wich commonly occurs in elderly.
PMCID: PMC3352183  PMID: 22611486
6.  Lack of Association between Recurrent Pregnancy Loss and Inherited Thrombophilia in a Group of Colombian Patients 
Thrombosis  2012;2012:367823.
Studies have shown an association between recurrent pregnancy loss and inherited thrombophilia in Caucasian populations, but there is insufficient knowledge concerning triethnic populations such as the Colombian. The aim of this study was to evaluate whether inherited thrombophilia is associated with recurrent pregnancy loss. Methods. We conducted a case-control study of 93 patients with recurrent pregnancy loss (cases) and 206 healthy multiparous women (controls) in a Colombian subpopulation. Three single nucleotide polymorphisms (SNPs) markers of the inherited thrombophilias factor V Leiden, prothrombin G20210A, and methylenetetrahydrofolate reductase C677T were genotyped by PCR-RFLP. Activated protein C resistance and plasma levels of antithrombin, protein C, and protein S were also measured. Results. The frequency of thrombophilia-associated SNPs, activated protein C resistance, and anticoagulant protein deficiencies, was low overall, except for the methylenetetrahydrofolate reductase C677T SNP. The differences between patients and controls had no statistical significance. Conclusion. Our study confirms the low prevalence of inherited thrombophilias in non-Caucasian populations and it is unlikely that the tested thrombophilias play a role in the pathogenesis of recurrent pregnancy loss in this Colombian population.
PMCID: PMC3345256  PMID: 22577540
7.  A Study of the Relationship between Weather Variables and Electric Power Demand inside a Smart Grid/Smart World Framework 
Sensors (Basel, Switzerland)  2012;12(9):11571-11591.
One of the main challenges of today's society is the need to fulfill at the same time the two sides of the dichotomy between the growing energy demand and the need to look after the environment. Smart Grids are one of the answers: intelligent energy grids which retrieve data about the environment through extensive sensor networks and react accordingly to optimize resource consumption. In order to do this, the Smart Grids need to understand the existing relationship between energy demand and a set of relevant climatic variables. All smart “systems” (buildings, cities, homes, consumers, etc.) have the potential to employ their intelligence for self-adaptation to climate conditions. After introducing the Smart World, a global framework for the collaboration of these smart systems, this paper presents the relationship found at experimental level between a range of relevant weather variables and electric power demand patterns, presenting a case study using an agent-based system, and emphasizing the need to consider this relationship in certain Smart World (and specifically Smart Grid and microgrid) applications.
PMCID: PMC3478798
Smart Grid; microgrid; Smart City; Smart Environment; Smart World; weather variables; electric power demand; sensor
8.  Spatial and Temporal Characteristics of the 2009 A/H1N1 Influenza Pandemic in Peru 
PLoS ONE  2011;6(6):e21287.
Highly refined surveillance data on the 2009 A/H1N1 influenza pandemic are crucial to quantify the spatial and temporal characteristics of the pandemic. There is little information about the spatial-temporal dynamics of pandemic influenza in South America. Here we provide a quantitative description of the age-specific morbidity pandemic patterns across administrative areas of Peru.
We used daily cases of influenza-like-illness, tests for A/H1N1 influenza virus infections, and laboratory-confirmed A/H1N1 influenza cases reported to the epidemiological surveillance system of Peru's Ministry of Health from May 1 to December 31, 2009. We analyzed the geographic spread of the pandemic waves and their association with the winter school vacation period, demographic factors, and absolute humidity. We also estimated the reproduction number and quantified the association between the winter school vacation period and the age distribution of cases.
The national pandemic curve revealed a bimodal winter pandemic wave, with the first peak limited to school age children in the Lima metropolitan area, and the second peak more geographically widespread. The reproduction number was estimated at 1.6–2.2 for the Lima metropolitan area and 1.3–1.5 in the rest of Peru. We found a significant association between the timing of the school vacation period and changes in the age distribution of cases, while earlier pandemic onset was correlated with large population size. By contrast there was no association between pandemic dynamics and absolute humidity.
Our results indicate substantial spatial variation in pandemic patterns across Peru, with two pandemic waves of varying timing and impact by age and region. Moreover, the Peru data suggest a hierarchical transmission pattern of pandemic influenza A/H1N1 driven by large population centers. The higher reproduction number of the first pandemic wave could be explained by high contact rates among school-age children, the age group most affected during this early wave.
PMCID: PMC3119673  PMID: 21712984
9.  Changes in the Viral Distribution Pattern after the Appearance of the Novel Influenza A H1N1 (pH1N1) Virus in Influenza-Like Illness Patients in Peru 
PLoS ONE  2010;5(7):e11719.
We describe the temporal variation in viral agents detected in influenza like illness (ILI) patients before and after the appearance of the ongoing pandemic influenza A (H1N1) (pH1N1) in Peru between 4-January and 13-July 2009.
At the health centers, one oropharyngeal swab was obtained for viral isolation. From epidemiological week (EW) 1 to 18, at the US Naval Medical Research Center Detachment (NMRCD) in Lima, the specimens were inoculated into four cell lines for virus isolation. In addition, from EW 19 to 28, the specimens were also analyzed by real time-polymerase-chain-reaction (rRT-PCR).
We enrolled 2,872 patients: 1,422 cases before the appearance of the pH1N1 virus, and 1,450 during the pandemic. Non-pH1N1 influenza A virus was the predominant viral strain circulating in Peru through (EW) 18, representing 57.8% of the confirmed cases; however, this predominance shifted to pH1N1 (51.5%) from EW 19–28. During this study period, most of pH1N1 cases were diagnosed in the capital city (Lima) followed by other cities including Cusco and Trujillo. In contrast, novel influenza cases were essentially absent in the tropical rain forest (jungle) cities during our study period. The city of Iquitos (Jungle) had the highest number of influenza B cases and only one pH1N1 case.
The viral distribution in Peru changed upon the introduction of the pH1N1 virus compared to previous months. Although influenza A viruses continue to be the predominant viral pathogen, the pH1N1 virus predominated over the other influenza A viruses.
PMCID: PMC2910706  PMID: 20668548
10.  Bone Mass and the CAG and GGN Androgen Receptor Polymorphisms in Young Men 
PLoS ONE  2010;5(7):e11529.
To determine whether androgen receptor (AR) CAG (polyglutamine) and GGN (polyglycine) polymorphisms influence bone mineral density (BMD), osteocalcin and free serum testosterone concentration in young men.
Methodology/Principal Findings
Whole body, lumbar spine and femoral bone mineral content (BMC) and BMD, Dual X-ray Absorptiometry (DXA), AR repeat polymorphisms (PCR), osteocalcin and free testosterone (ELISA) were determined in 282 healthy men (28.6±7.6 years). Individuals were grouped as CAG short (CAGS) if harboring repeat lengths of ≤21 or CAG long (CAGL) if CAG >21, and GGN was considered short (GGNS) or long (GGNL) if GGN ≤23 or >23. There was an inverse association between logarithm of CAG and GGN length and Ward's Triangle BMC (r = −0.15 and −0.15, P<0.05, age and height adjusted). No associations between CAG or GGN repeat length and regional BMC or BMD were observed after adjusting for age. Whole body and regional BMC and BMD values were similar in men harboring CAGS, CAGL, GGNS or GGNL AR repeat polymorphisms. Men harboring the combination CAGL+GGNL had 6.3 and 4.4% higher lumbar spine BMC and BMD than men with the haplotype CAGS+GGNS (both P<0.05). Femoral neck BMD was 4.8% higher in the CAGS+GGNS compared with the CAGL+GGNS men (P<0.05). CAGS, CAGL, GGNS, GGNL men had similar osteocalcin concentration as well as the four CAG-GGN haplotypes studied.
AR polymorphisms have an influence on BMC and BMD in healthy adult humans, which cannot be explained through effects in osteoblastic activity.
PMCID: PMC2902510  PMID: 20634949
11.  Influenza-Like Illness Sentinel Surveillance in Peru 
PLoS ONE  2009;4(7):e6118.
Acute respiratory illnesses and influenza-like illnesses (ILI) are a significant source of morbidity and mortality worldwide. Despite the public health importance, little is known about the etiology of these acute respiratory illnesses in many regions of South America. In 2006, the Peruvian Ministry of Health (MoH) and the US Naval Medical Research Center Detachment (NMRCD) initiated a collaboration to characterize the viral agents associated with ILI and to describe the clinical and epidemiological presentation of the affected population.
Methodology/Principal Findings
Patients with ILI (fever ≥38°C and cough or sore throat) were evaluated in clinics and hospitals in 13 Peruvian cities representative of the four main regions of the country. Nasal and oropharyngeal swabs, as well as epidemiological and demographic data, were collected from each patient. During the two years of this study (June 2006 through May 2008), a total of 6,835 patients, with a median age of 13 years, were recruited from 31 clinics and hospitals; 6,308 were enrolled by regular passive surveillance and 527 were enrolled as part of outbreak investigations. At least one respiratory virus was isolated from the specimens of 2,688 (42.6%) patients, with etiologies varying by age and geographical region. Overall the most common viral agents isolated were influenza A virus (25.1%), influenza B virus (9.7%), parainfluenza viruses 1, 2, and 3, (HPIV-1,-2,-3; 3.2%), herpes simplex virus (HSV; 2.6%), and adenoviruses (1.8%). Genetic analyses of influenza virus isolates demonstrated that three lineages of influenza A H1N1, one lineage of influenza A H3N2, and two lineages of influenza B were circulating in Peru during the course of this study.
To our knowledge this is the most comprehensive study to date of the etiologic agents associated with ILI in Peru. These results demonstrate that a wide range of respiratory pathogens are circulating in Peru and this fact needs to be considered by clinicians when treating patients reporting with ILI. Furthermore, these data have implications for influenza vaccine design and implementation in South America.
PMCID: PMC2700970  PMID: 19568433

Results 1-11 (11)