Income Mobility in Latin America

[Excerpt] In the last decades Latin American countries have experienced substantial macroeconomic instability. While the region as a whole experienced economic growth during most of the 1990’s and 2000’s, there were also years of stagnation as well as economic decline

Earnings Mobility in Argentina, Mexico, and Venezuela: Testing the Divergence of Earnings and the Symmetry of Mobility Hypotheses

This paper examines changes in individual earnings during positive and negative growth periods in three Latin American economies: Argentina, Mexico, and Venezuela. We ask whether those individuals who start in the best economic position are those who experience the largest earnings gains or the smallest earnings losses; this is the “divergent mobility” hypothesis. We also compare periods of positive economic growth with those of negative economic growth, asking whether those groups of individuals that experience large positive earnings gains when the economy is growing are the same as those that experience large earnings losses when the economy is contracting; this is the “symmetry of mobility” hypothesis. We find very occasional support for the divergent mobility hypothesis in scattered years in the cases of Mexico and Venezuela, and no support at all in the case of Argentina. Rather, earnings mobility is most frequently convergent or neutral in all three countries. As for the symmetry of mobility hypothesis, we find that it is rejected in most cases; rather, those groups that gain the most when the economy is growing are also the ones that gain the most when the economy is contracting. Furthermore, we explain how the absence of divergence is compatible with rising inequality in the countries under study

Chronic social stress induces peripheral and central immune activation, blunted mesolimbic dopamine function, and reduced reward-directed behaviour in mice

Psychosocial stress is a major risk factor for depression, stress leads to peripheral and central immune activation, immune activation is associated with blunted dopamine (DA) neural function, DA function underlies reward interest, and reduced reward interest is a core symptom of depression. These states might be inter-independent in a complex causal pathway. Whilst animal-model evidence exists for some specific steps in the pathway, there is currently no animal model in which it has been demonstrated that social stress leads to each of these immune, neural and behavioural states. Such a model would provide important existential evidence for the complex pathway and would enable the study of causality and mediating mechanisms at specific steps in the pathway. Therefore, in the present mouse study we investigated for effects of 15-day resident-intruder chronic social stress (CSS) on each of these states. Relative to controls, CSS mice exhibited higher spleen levels of granulocytes, inflammatory monocytes and T helper 17 cells; plasma levels of inducible nitric oxide synthase; and liver expression of genes encoding kynurenine pathway enzymes. CSS led in the ventral tegmental area to higher levels of kynurenine and the microglia markers Iba1 and Cd11b and higher binding activity of DA D1 receptor; and in the nucleus accumbens (NAcc) to higher kynurenine, lower DA turnover and lower c-fos expression. Pharmacological challenge with DA reuptake inhibitor identified attenuation of DA stimulatory effects on locomotor activity and NAcc c-fos expression in CSS mice. In behavioural tests of operant responding for sucrose reward validated as sensitive assays for NAcc DA function, CSS mice exhibited less reward-directed behaviour. Therefore, this mouse study demonstrates that a chronic social stressor leads to changes in each of the immune, neural and behavioural states proposed to mediate between stress and disruption of DA-dependent reward processing. The model can now be applied to investigate causality and, if demonstrated, underlying mechanisms in specific steps of this immune-neural-behavioural pathway, and thereby to identify potential therapeutic targets

MMP-13 is constitutively produced in human chondrocytes and co-endocytosed with ADAMTS-5 and TIMP-3 by the endocytic receptor LRP1

Matrix metalloproteinase 13 (MMP-13) degrades collagenous extracellular matrix and its aberrant activity associates with diseases such as arthritis, cancer, atherosclerosis and fibrosis. The wide range of MMP-13 proteolytic capacity suggests that it is a powerful, potentially destructive proteinase and thus it has been believed that MMP-13 is not produced in most adult human tissues in the steady state. Present study has revealed that human chondrocytes isolated from healthy adults constitutively express and secrete MMP-13, but that it is rapidly endocytosed and degraded by chondrocytes. Both pro- and activated MMP-13 bind to clusters II and III of low-density lipoprotein (LDL) receptor-related protein 1 (LRP1). Domain deletion studies indicated that the hemopexin domain is responsible for this interaction. Binding competition between MMP-13 and ADAMTS-4, -5 or TIMP-3, which also bind to cluster II, further shown that the MMP-13 binding site within cluster II is different from those of ADAMTS-4, -5 or TIMP-3. MMP-13 is therefore co-endocytosed with ADAMTS-5 and TIMP-3 by human chondrocytes. These findings indicate that MMP-13 may play a role on physiological turnover of cartilage extracellular matrix and that LRP1 is a key modulator of extracellular levels of MMP-13 and its internalization is independent of the levels of ADAMTS-4, -5 and TIMP-3

Identification of diagnostic serum protein profiles of glioblastoma patients

Diagnosis of a glioblastoma (GBM) is triggered by the onset of symptoms and is based on cerebral imaging and histological examination. Serum-based biomarkers may support detection of GBM. Here, we explored serum protein concentrations of GBM patients and used data mining to explore profiles of biomarkers and determine whether these are associated with the clinical status of the patients. Gene and protein expression data for astrocytoma and GBM were used to identify secreted proteins differently expressed in tumors and in normal brain tissues. Tumor expression and serum concentrations of 14 candidate proteins were analyzed for 23 GBM patients and nine healthy subjects. Data-mining methods involving all 14 proteins were used as an initial evaluation step to find clinically informative profiles. Data mining identified a serum protein profile formed by BMP2, HSP70, and CXCL10 that enabled correct assignment to the GBM group with specificity and sensitivity of 89 and 96%, respectively (p < 0.0001, Fischer’s exact test). Survival for more than 15 months after tumor resection was associated with a profile formed by TSP1, HSP70, and IGFBP3, enabling correct assignment in all cases (p < 0.0001, Fischer’s exact test). No correlation was found with tumor size or age of the patient. This study shows that robust serum profiles for GBM may be identified by data mining on the basis of a relatively small study cohort. Profiles of more than one biomarker enable more specific assignment to the GBM and survival group than those based on single proteins, confirming earlier attempts to correlate single markers with cancer. These conceptual findings will be a basis for validation in a larger sample size

Genomic epidemiology reveals multiple introductions of Zika virus into the United States

Zika virus (ZIKV) is causing an unprecedented epidemic linked to severe congenital abnormalities. In July 2016, mosquito-borne ZIKV transmission was reported in the continental United States; since then, hundreds of locally acquired infections have been reported in Florida. To gain insights into the timing, source, and likely route(s) of ZIKV introduction, we tracked the virus from its first detection in Florida by sequencing ZIKV genomes from infected patients and Aedes aegypti mosquitoes. We show that at least 4 introductions, but potentially as many as 40, contributed to the outbreak in Florida and that local transmission is likely to have started in the spring of 2016-several months before its initial detection. By analysing surveillance and genetic data, we show that ZIKV moved among transmission zones in Miami. Our analyses show that most introductions were linked to the Caribbean, a finding corroborated by the high incidence rates and traffic volumes from the region into the Miami area. Our study provides an understanding of how ZIKV initiates transmission in new regions

Why Is There a Lack of Consensus on Molecular Subgroups of Glioblastoma? Understanding the Nature of Biological and Statistical Variability in Glioblastoma Expression Data

Gene expression patterns characterizing clinically-relevant molecular subgroups of glioblastoma are difficult to reproduce. We suspect a combination of biological and analytic factors confounds interpretation of glioblastoma expression data. We seek to clarify the nature and relative contributions of these factors, to focus additional investigations, and to improve the accuracy and consistency of translational glioblastoma analyses.We analyzed gene expression and clinical data for 340 glioblastomas in The Cancer Genome Atlas (TCGA). We developed a logic model to analyze potential sources of biological, technical, and analytic variability and used standard linear classifiers and linear dimensional reduction algorithms to investigate the nature and relative contributions of each factor.Commonly-described sources of classification error, including individual sample characteristics, batch effects, and analytic and technical noise make measurable but proportionally minor contributions to inconsistent molecular classification. Our analysis suggests that three, previously underappreciated factors may account for a larger fraction of classification errors: inherent non-linear/non-orthogonal relationships among the genes used in conjunction with classification algorithms that assume linearity; skewed data distributions assumed to be Gaussian; and biologic variability (noise) among tumors, of which we propose three types.Our analysis of the TCGA data demonstrates a contributory role for technical factors in molecular classification inconsistencies in glioblastoma but also suggests that biological variability, abnormal data distribution, and non-linear relationships among genes may be responsible for a proportionally larger component of classification error. These findings may have important implications for both glioblastoma research and for translational application of other large-volume biological databases

Development of an integrated system for activity-based profiling of matrix metallo-proteases

Matrix metallo-proteases constitute a family of extracellular zinc-dependent endopeptidases that are involved in degradation of extracellular matrix (ECM) components and other bioactive non-ECM molecules. A plethora of studies have implicated important roles for MMPs in many diseases (including cancer and chronic inflammatory diseases) and normal biological processes. Our understanding of the complex roles of MMPs is, however, still limited, which is illustrated by the poor performance of broad-spectrum MMP inhibitors in clinical trials. The regulation of MMP activity by post-translational mechanisms is a complicating factor in MMP biology and pathology, and diminishes the effectiveness of conventional "expression-based" proteomic methods to study MMPs. The ability to profile MMPs based on functionally related activities would greatly facilitate research about their involvement in pathological processes. This thesis describes the development of a liquid chromatography-mass spectrometry-based integrated system for the selective detection of active MMPs in complex biological samples. Throughout the thesis, purified recombinant MMP-12 (catalytic domain) is used as a model enzyme. Chapter 2 demonstrates the feasibility of activity-based MMP-12 enrichment through batch extractions with an immobilized inhibitor affinity sorbent. A broad-range MMP inhibitor (PLG-NHOH) was immobilized on a Sepharose support with a ligand density of 9.8 mmol/L. The functionality of the inhibitor after immobilization was demonstrated with batch extractions of MMP-12 added to buffer, resulting in extraction yields around 97%. Quantification was done indirectly using an activity assay to determine unbound MMP-12. Active MMP-12 could also be selectively extracted when added to serum (after inactivation of the endogenous inhibitor α2-macroglobulin with trypsin) at a low level. Experiments with the endogenous inhibitors TIMP-1 and α2-macroglobulin revealed that MMP-12 extraction is strictly activity-dependent. Chapter 3 considers the automation of the extraction which is needed for on-line coupling to downstream analytical steps. Samples containing MMP-12 in buffer were extracted at different flow rates using cartridges packed with inhibitor affinity sorbent. Besides faster extractions and a reduced number of manual manipulations, higher extraction yields (98.9% - 99.3%) were obtained over the whole flow rate range compared to batch extractions. Application of the method to synovial fluid from a rheumatoid arthritis patient followed by gelatin-zymography revealed a strong enrichment of distinct MMPs from this biological sample that were not clearly visible in the original sample. The use of an auto-sampler and a solid-phase extraction (SPE) workstation allowed full automation of the extraction procedure. MMP-12 extractions were optimized, showing that ligand density is an important factor with a clear extraction yield optimum around 4 to 10 mmol/L. Conditioning of the Sepharose affinity sorbent for 1 week prior to use resulted in a further increase in extraction yield. Under optimal conditions, an extraction yield of 99.5% was reached with a cartridge contact time of only 13 s for MMP-12. The efficacy of the extraction method for activity-based MMP profiling was further improved by the use of a broad-spectrum MMP inhibitor with nmol/L affinity (TAPI-2), which resulted in increased extraction yields for all tested MMPs. Extraction yields ranging from 98.8% to 99.8% were obtained for MMP-1, -7, -8, -10, -12, and -13, while for MMP-9 (full length and catalytic domain) extraction yields of 96.1% and 98.4% were reached (all at a cartridge contact time of 19 s). This effective enrichment of MMPs illustrates the possibility to enrich from dilute samples with low levels of endogenous MMPs. In Chapter 4, we investigated the chemical modification (acetylation) of immobilized trypsin (on a Sepharose and a polystyrene support) for enhanced digestion efficacy in integrated protein analysis platforms. Complete digestion of cytochrome c was obtained with modified-trypsin beads with a contact time of only 4 sec, while corresponding unmodified-trypsin beads gave incomplete digestion. The digestion rate of myoglobin, a protein known to be rather resistant to proteolysis, was not altered by acetylating trypsin and required a buffer containing 35% acetonitrile to obtain complete digestion. The use of acetylated-trypsin beads led to fewer interfering tryptic autolysis products, indicating an increased stability of this modified enzyme. Importantly, the modification did not affect trypsin's substrate specificity, as the peptide map of myoglobin was not altered upon acetylation of immobilized trypsin. Kinetic digestion experiments in solution with low-molecular-weight substrates and with cytochrome c confirmed the increased catalytic efficiency (lower KM and higher kcat and increased resistance to autolysis of trypsin upon acetylation. Because of the increased trypsin activity, the digestion rate is enhanced, which facilitates on-line digestion of low-abundance proteins with higher yields and in less time. These are favourable properties of the modified trypsin reactor and should make it a valuable tool in automated protein analysis systems. Chapter 5 deals with the implementation of the extraction and the digestion cartridge into an integrated system for automated, activity-based profiling of MMPs. Enrichment was followed by on-line digestion in an immobilized acetylated trypsin reactor. Hyphenation of the sample pre-treatment steps to a nanoLC-MS system was achieved by loading tryptic MMP-12 peptides on a reversed-phase trap column, followed by backflush elution to a 50-µm reversed-phase silica-based monolith capillary column coupled to a nanoESI interface and an ion trap mass spectrometer. The use of non-ionic surfactants in the sample pre-treatment steps resulted in better sensitivity, probably because on-line digestion efficiency is improved and non-specific adsorption is suppressed. The completely automated method is able to analyse a sample every 75 min. Spiking of MMP-12 at 4 pmol into 500 µL urine resulted in selective detection of tryptic MMP-12 peptides with high intensities. At sub-pmol MMP-12 levels the signal dropped strongly, but some tryptic MMP-12 peptides were still detected at 0.25 pmol in 100 µL injections (from buffer) with good signal-to-noise ratios. Though the developed system has not been extensively tested with biological samples to detect active endogenous MMPs, several aspects should likely be improved in order to achieve this. One important limiting factor in obtaining low or sub-fmol sensitivity is probably the rate of digestion in the trypsin reactor. Despite the relatively high concentration of immobilized trypsin and the chemical modification, the digestion rate is still limited by the protein substrate concentration (due to Michaelis-Menten kinetics). The use of support materials with less diffusional transport limitations such as monolithic materials in both the enrichment and the digestion step will likely result in improved digestion rates at low MMP concentrations. Captured MMPs can be eluted from a monolithic extraction cartridge in a smaller volume and thus be digested at higher concentration in digestion reactor, resulting in improved digestion kinetics. Reduced diffusional transport limitation in the trypsin reactor may also contribute to a further improvement of the digestion kinetics at low MMP concentrations. Digestion kinetics may also be further improved through the investigation of other types of chemical modifications of immobilized trypsin. Hydrophilic protein modifications generally result in an enhanced thermal stability and may permit the use of elevated digestion temperatures to achieve faster digestion kinetics. A decreased binding of hydrophobic peptides to immobilized trypsin, resulting in higher peptide yields and a lower carry-over is an additional advantage of hydrophilic modifications. Chapter 5 demonstrated a positive effect of non-ionic surfactant additions to the extraction and digestion buffers on the mass spectrometric MMP-12 peptide signals. Yet, higher levels of these surfactants have an adverse effect on the effective capacity (due to overloading) of the reversed-phase trap column and will pollute the ESI interface. The option to include an ion-exchange step, either on- or off-line to wash away high levels of surfactant prior to reversed-phase trapping, should thus be a subject of further research. Care must to be taken, however, not to introduce too many system steps, which would result in high system complexity accompanied by low robustness. Validation (LOD, LOQ, day-to-day and intra-day variation) of the integrated analytical system should be performed before application to clinical studies, once the system has been further optimized. The aspect of quantification of detected MMPs should also be addressed in future research. To correct for different yields of the different steps, ideally an internal standard with a known concentration, added to the biological sample, should be used. This can be achieved by using isotopically labelled MMPs (produced by expression in a host organism which is grown on 15N-enriched medium). To broaden the applicability of the developed system to a more diverse group of metallo-proteases, the use of affinity sorbents with a cocktail of immobilized metallo-protease inhibitors targeting different types of enzymes can be investigated. Through the use of affinity sorbents targeting completely different protein classes (of low abundance), the developed system can be potentially applied in a wide range of studies. The requirement for different elution conditions with each type of affinity sorbent affects the on-line coupling with the digestion reactor and is the main step which needs to be evaluated before the system can be used to analyse other protein classes. Digestion reactors with immobilized proteases, other than trypsin, may be required to ensure elution-digestion compatibility.